React OS:Here comes the Windows Nemesis!

images.jpegReactOS is a free and open-sourced operating system based on the Windows architecture, providing support for existing applications and drivers, and an alternative to the current dominant consumer operating system.

ReactOS 0.3.1 Mainly, the work focused on rewriting certain parts of the ReactOS Core (kernel, HAL, bootloader, etc). It’s very hard to sum up the huge Changelog in an outline, but briefly:

  • Freeldr was improved
  • HAL’s key areas have been significantly improved (irql-related, bus support, kd-functions)
  • The Kernel experienced a massive rewrite of incompatible parts (and is still in the process of improvement)
  • Run-time library (Rtl) got a lot of improvements and bugfixes
  • Bugs were fixed in kernel-mode drivers and a better USB driver was added
  • Registry-support has been greatly improved thanks to addition of “cmlib”, a library shared by the boot loader and the kernel to handle binary registry hives; it even supports binary registry hives created by Windows
  • More fixes in the Win32 subsystem and user-mode DLLs
  • Boot video driver (and a splash screen) was added

Read through the changelog, and you will see the amount of changes in this release!
However, there are a few things worth mentioning. First of all, please don’t forget this is an alpha-stage operating system, which means it is not suitable to replace your main OS (due to stability and compatibility concerns). And second, this release is aimed to be run mostly in virtualizers / emulators (like QEmu, VMWare, Parallels, etc): because of the big amount of changes, our development team was not able to test/fix all problems which arise when running ReactOS on real hardware.

Note: This project is still in Alpha state .. But has shown massive improvements which is a good point.

Download: React OS
More Screen Shots: Click Here


71 Responses to “React OS:Here comes the Windows Nemesis!”

  1. Anuj Gsrg Says:

    finally we will have something running everything @ not pirated for free hopefully

  2. Top Posts « Says:

    […] React OS:Here comes the Windows Nemesis! [image]ReactOS is a free and open-sourced operating system based on the Windows architecture, providing support for […] […]

  3. norfaizn Says:

    woah awesome dude..hopefully this one will always be an open source program 😀

  4. awalsadja Says:

    React OS? MMM new for me…
    looks interesting, im begin downloading

  5. riv Says:

    ahh… this is good news.
    ill give it a try 🙂

  6. kamisama Says:

    Awesome work people, keep it up.

  7. TJ Says:

    Hmm, got a list of what works and what doesn’t?

    would be handy for everyone to put in..

  8. Max Malm Says:

    Finally! 🙂

  9. politicalslug Says:

    If this is what it claims to be, it’ll get shut down by Microsoft (via the courts) before it ever reaches beta. There’s no way this product could function as it claims to without infringing on at least fifty plus of Microsoft’s patents. Guys, I don’t even know why you’re wasting your time with this when its fate is so clear.

  10. eBooksBay Says:

    Very good new, gone try that. 🙂

  11. sazwqa Says:

    well i have tried it and all that I can say is that I feel it’s not too upto the mark, somehow developers deserve the praise for their painstaking efforts but i feel there are better things out there to put your mind.


  12. asdf Says:

    ReactOS has been lingering around for years… every once in a while you see a blog post like people hoping this projects makes a push forward.

    Keep dreaming.

  13. Steve Says:

    ReactOS is almost a dream come true. If it reaches a stable release, it will instantly get tens of millions of users, there’s no doubt about it, but how long will it take? Maybe too long…

  14. Marv Says:

    I can not wait to give this a try, expect a full review as soon as I can 🙂

  15. nomadz Says:

    is there any date for a stable version?

  16. Brian cee Says:

    My God where has this been this is the best find for a long time

    I am so glad somebody has made this free and open source lets hope it stays that way.

    I’m getting it

  17. roktiw Says:

    looking forward to beta :]

  18. Paulimus Prime Says:

    I can see heads exploding in Redmond haha!

  19. anonymous Says:

    Thank you

  20. Confused Says:

    I have a BAD feeling that microsoft will flip out about “patent” infringements. Especially since the start bar thing actually directly mimics WIN.

  21. Matt Says:

    Be prepared to get sued.

  22. hedgehog Says:

    I’m grabbing the source code for this project before publicity becomes its undoing.

    If ReactOS has, indeed, been around for years that’s great. The second MS sees it as a threat, they’ll definitely exercise their patents.

    It could be fun to play around with this alpha. I’ll make a virtual machine now 😀

  23. David Says:

    Of course Microsoft’s software patents don’t apply in Europe. So perhaps the OS will only be unusable in the US…. doesn’t mean to say the rest of us have to miss out.

  24. rhY Says:

    Jesus, you guys are all FUD! ROS is a cool project that has a LOT of promise and is under very heavy and active dev right now. It is still alpha, but the next release should be a LOT better, based on what I’ve been reading in irc and elsewhere.

    The truth is Windows can not keep up with FOSS development models. Vista vs. Ubuntu illustrates this quite clearly. Expect ROS to be the only windows anyone uses in 5 years.

  25. 1066884 Says:

    Simply amazing. I hope you can manage to keep this going for a long time.

    I’m grabbing it now – Thank You!

  26. The Source Computing Blog » React OS:Here comes the Windows Nemesis! Says:

    […] applications and drivers, and an alternative to the current dominant consumer operating more | digg […]

  27. Mandinga Says:

    oh no, Why would anyone want to clone windows????!!!

  28. Dark Star Says:

    Thanks for the comments buddies 🙂 React Os mybe calleed Clone .. never mind it … The main advantage of ROS is that its free and you need not to spend lots of money 😉 if you are not Linux fan :P. This gave a better alternative for thos ewho did not like tuxing 😛

  29. GOGRIN Says:

    Woot Unreal Tournament runs on it!

    My House!

  30. Greg Newell Says:

    Wow! An operating system just like WINDOWS only worse! Free is all you’ll get for the effort. Anybody trying it already has windows and wants to compare. Let’s be real, anybody wanting windows for free can get it…you don’t need a clone. The tragedy is that the caliber of programmers reinventing this technology could probably produce something really great!

  31. cheaperholidays Says:

    Hey well done guys, its that Darwinian theory all over again lets hope you give Gates a bit a shock, smug git


  32. Pensador Says:

    It sure looks promising!

  33. tom Says:

    ha! its fruitless…..when they and IF they get it working like it should……here comes bill, changes the specs…….and reverse engeneering has to start again…

  34. Ashvala Vinay Says:

    What is going on here? just like vista was copied from Mac OS X…(May be a little interface problem). I am pro Mac. It is copying that makes that diffrence. If Windows had the courage that the people will trust them & make windows opensource, it comes of no use to open source a closed product. Mac may be hacked because it runs a open source kernel. FYI Mac runs Darwin & Free BSD. It is not good to copy other OS just to make it open source.

    Please report if the comment was a little harsh 😀

    My rating for React OS will be 3/10

    Ashvala Vinay

  35. Dhonn Says:

    Nice. But they should have build the thing on top of the Linux kernel and simply build a NT kernel virtual machine (like Java) for kernel space and WINE for user space API.

    Hey just because this project is a clone of windows doesn’t mean it violates any patents or copyrights. It was independently programmed without the use if windows source code.

  36. Claudio Says:

    I assume that all of you read the part on the website that states the following:

    “Please bear in mind that ReactOS 0.3.1 is still in alpha stage, meaning it is not feature complete and is not recommended for everyday use.

    This is still in alpha. Remember that before you knock it. It’s not easy to reverse-engineer something as large as Windows. They have to make sure that they do not infringe on anything that’s intellectual property of MS and make sure that it still works as genuinely as Microsoft’s OS.

    It’s also a project that’s been around a long time, back when they were trying to clone the Windows NT kernel. They eventually decided to scrap that and start from scratch with something that’s more parallel to the Windows XP kernel.

    And although I’m not a Windows fan, I definitely welcome a completely open-sourced Windows clone. Maybe some good would come out of it considering Microsoft’s lackluster track record with its consumers.

  37. Ken Says:

    I’m not sure I understand how an OS can be “based on the Windows architecture” and maintain itself as free and legal. I suppose the publicly available API might be good for something, but publishing an actual OS is sure to make MS hot under the collar whether they have a case or not.

  38. Zac Davis Says:

    I was just about to write a post on this, I would like to say that reverse engineering Windows is no doubt illegal, you agreed to not do that in the license. Just like you agreed to not use iTunes to create nuclear bombs when you installed it. Yeah, that’s actually true. Too bad that once Microshit gets word of this, they will seek out any and all legal action possible against it.

  39. Terry Lechecul Says:

    > operating system based on the Windows architecture

    I have one question:


  40. Claudio Says:


    Isn’t WINE a reverse-engineered effort to reproduce the Windows APIs in order to run the applications on non-Windows operating systems? If what you’re saying is correct, then projects like those from Transgaming and Crossover Office face some serious problems. They’ve been in existence and in the public eye for quite a while now, even moreso with the announcement of EA games being run in Transgaming’s Cider on OS X.

    Most of what is being done in ReactOS is done on top of the work done with WINE. They are basically trying to reproduce a working Windows-like environment using WINE more-or-less.

    And what’s wrong with an operating system that’s open source being similar to a commercial one? Linux and the *BSDs are all derived from UNIX in one way or another. I guess neither Apple or MS should have made their operating system’s similar to Xerox’s, although that scenario is a bit different.

  41. goch1988 Says:

    Nice work but why stick with Windows logo?

  42. Marian Says:

    Wow, this system will be great.

  43. dragonopolis Says:

    Give them a break people. Like people have commented as well as ReactOS themselves have said its in an early Alpha stage. Of course it isn’t going to run like full blown XP with 2 major updates. The idea has merit. Microsoft can’t touch them because ReactOS is not a clone. They have there own kernel that just so happens to be designed to be able to run win32 apps natively. For instance, there are a lot of FPSs and none of them are not clones but have many similarities (example how many human vs alien FPSs are there or how about War FPSs). If you get my point, The type FPS = OS and the Basic out lying theme (Human vs Alien) = Win32 apps. Everything else, all the underlying stuff, would be different.

    Some people have tried to make a case that ReactOS is just a self running wine. Nope. Linux runs wine but wine is not Linux. In other words. ReactOS has taken wine and ported over to their kernel. This probably helps speed up the development. Since their kernel is suppose to run win32 apps natively ReactOS version of wine will be probably will be a lot smaller than Linux and be used for things like DirectX compatibility. Theoritcally, an app that requires wine (like a game) should run better and be more stable on ReactOS than on Linux running wine. Once ReactOS is, of course, stable.

    Open sourcing the code is good. Should make ReactOS easier and faster to patch and make it more secure than Win2000/XP ever was.

    The only negative side I really see is that these guys are way behind the times. Still stuck in a 32 bit world they better have this OS up and running by 2009 max and already have a 64 bit version on its way. In ReactOS defense, 64 bit is having a slow start among the other operating systems. This is both the OS’s fault and the developers. Linux has had 64 bit version for years but still seems to be an after thought in their community rather than mainstream. Microsoft just screw up the 64 bit transition. I personally believe Vista’s ability to run all 64 bit apps smoothly won’t happen until the first service pack is out. Apple has been running 64 bit “under the hood” so to speak in Tiger. Leopard is suppose to bring 64 bit to the User. In theory, Apples transitions to an all 64 bit OS should be smoother. ReactOS needs to get this OS out soon and start working on a 64 bit version as well as the ability to take advantage of multi-processors or it will die a quick death.

    From what I read from their site the long term plans will include expanding its OS beyond Win32 eventually create its own identity.

    I wish these guys the best of luck!

  44. Jonathan Says:

    I’m waiting on the Beta release before I install it on my parents’ computer. Right now they’re running Debian! 🙂

  45. Mehzor Says:

    @ terry
    If it is based on the same architecture then all the same programs will run on it, if it is open source then people will help make it run stable and faster. Pretty much your making a new OS that comes with a software libaray that is one of the largest in the world

    I ran it on the VMware emulation:
    Over all thoughts, fast load (only 70mb OS!!), very unstable (welcome to alpha), and there are a lot of things that still need to be addressed (no download progress window/meter in any browser).

    Nice job guys, keep up the good work, I hope in a year or so I will be able to replace M$ with react.

  46. Beatdown Says:

    This isn’t new gang, so for all of you asking questions like “why” or “Microsoft will shut it down” you are way behind the curve. Certainly Wine hasn’t been shut down yet either.

    My complements to the team for the progress on the latest release.

  47. Samir Benahmed Says:

    How can this be open-source? Surely this operating system defies the very purpose of open-source as it is ‘based on the Windows architecture’. Why on Earth would you would you want this operating system? It’s probably got more security holes and bugs than existing Microsoft operating system and it’s not had any money invested into it. Microsoft will get this thing shutdown in no time, thats if before the developers don’t stop working on it cos of boredom.

  48. George Says:

    I second the question…why? If you want something free, get one of the many flavors of Linux and have fun installing the beast. Otherwise, just spend the money and buy the real thing. And don’t say ‘…can’t afford…’ because you can. If you are using anything remotely resembling a modern pc, then you can afford to buy any of the flavors of Windows and not worry about it being compatible. You can buy it for your price…you might actually have to work to find it though…something many probably won’t do and just complain about it. Seriously, get Ubuntu and download one of the Vista/XP/Classic themes and mimick Windows. Or get a Mac.

  49. Stuart Loxton Says:

    They are taking the wrong way, they shouldn’t be aiming to make a free version of Windows, whats the point? Same bugs, same virus’s thats alot of time wasted! They should be making a way of running Windows stuff on Linux so more people start the swap!

  50. Seronis Says:

    @’one question, why?’

    Well because they can write the subsystems from scratch, in a manner that isnt prone to memory leaks or corruption. They can do more effecient memory management. They can do more effecient file system search. They can remove ‘bloat’ out of how different aspects of an OS are organized. They dont have to design Win9x and then upgrade, they are just going straight for WinXP binary compatibility. Microsoft plans on phasing out XP as fast as they can, they want to push their DRM/virus laden Vista to everyone possible. Many people do NOT want to ever go the vista route. Myself included. I have XP ru nning along with Ubuntu. I check out progress of MenuetOS and ReactOS on occasion (even EROS). So the advantage of having ROS available is that it will be available for free. legally, to any person or company, for eternity. And it will support a platform that is already preferred by many not willing to give linux a shot.

    @’reverse engineering is illegal…’
    reverse engineering is explicitely protected by copyright and patent law. So is making products that are meant to be compatible with others. The ROS devs just have to avoid explicite patent issues, and an API in and off itself has already been determined to be non protected. Just the implimentation can be protected. That is why there are versions of SUSE that run on the PS2, GameCube and XBox, that are legal.

    @’build on top of linux / wine’

    If you read the website there are multiple members who do joint work on both WINE and ROS, but ROS isnt a VM or EMU. Its a full OS that just happens to be binary compatible with windows programs. if you want that in perspective is the same way that programs compiled under different versions of *nix are mostly able to be run on other *nix variants.

    @’bill comes and changes the specs…’

    Non issue. There is no goal of being compatible with Vista or future M$ variants. This is meant to be an improvement / extension of an XP environment.

    And as far as the comment on ROS taking over the windows market in 5 years, I might put it at 10-15 and be believable. But they have a lot of work left to do currently and no where near the staff that created the original Windows. So 5 years is too generous (though they do deserve quite some credit).

  51. Mauro Andres Says:

    True and I second it. Why?!?!

  52. Aaron Says:

    @Mauro Andres

    Because it will help people that only use Windows because it is familiar to switch. it is hard to convince the average user to learn a new operating system and explore the depths of the command line.

  53. grepgames Says:

    To give another answer to “why”:

    Because Linux is great and open-source alternatives exist for almost every proprietary application, but sometimes there just isn’t an acceptable alternative for a specific program, particularly if you’re doing business with someone who’s expecting files in a specific format. (The programs I can’t do without are Finale and Sibelius, but other people might have the same issue with Pro Tools, Final Cut Pro, Photoshop, &c.) The old solution is to dual-boot, which is a pain. The newer solution is to VM, which is less of a pain (or WINE, if your program works in WINE). I would love for ROS to get to the point that I could VM it for my Windows apps because 1) I don’t need to buy or crack a license to run it, 2) It will undoubtedly be more VM-friendly, i.e. not freak out if I tweak the specs on my VM, and 3) Because it’s a newer OS which hasn’t already accumulated years of cruft, it will probably boot faster and take less system resources than Windows.

    Or to answer “why” more concisely:
    Starcraft 2 without Windows

  54. Ken Says:

    ReactOS? First time heard of it.

    Well, if this OS can work with all my existing Windows programs and I don’t have to worry about viruses/spyware/malware, I will switch to it and throw Windows away for good. But don’t think that’s possible.

    Based on Windows architecture that means it’s almost the same as Windows except that it is free… so I don’t see any point of using it at all.

    Yes, get a Mac or Ubuntu.

  55. indiefatigable Says:

    Yeah, this is great for people who want to run windows on a VM without buying a license for it. But if Microsoft comes down hard on this one with patent violations and makes it illegal to download, wouldn’t people just download a real windows OS illegaly?
    Besides, why would you want to look at a source code that compiles into Windows! If you like fiddling with your code, switch to linux, that’s what it’s for.
    If people are going to use this to run proprietary software like office and photoshop that they can’t do without, then any cost savings with this free OS will be completely offset by the costs of these expensive softwares. If you are really going to buy these proprietary softwares you may be better off getting similar (in some cases better) alternatives for your primary OS.

  56. Francis Says:

    Until we actually get a Stable Release put , tested with 80% of windows apps, i think i will not even test it. Alpha is just a game or demo (lab) state. Let us know !

  57. Mauro Andres Says:

    As far as being an intermediate OS to enable an eventual switch to Gnu-Linux (or a BSD), this may just postpone using the better system they should be learning anyway, assuming that they care about stability and security.

    Not t put down this tremendous effort.

    There used to be a system called Free Dos that provided a free and compatible OS to m$’s DOS, while we’re mentioning m$ clones.

  58. showmescifi Says:

    With each release it keeps getting btr

    “”ReactOS kernel was started 10 years ago, and we still have some code of that date. “

  59. why Says:

    I agree, why? tremendous efforts and it’s like putting your testicles in a guillotine, and let bill gates control it. microsoft can sue the project, change the specs of windows (reactOS aim to be compatible with XP? when the project will be completed, xp will be unsupported by windows applications).
    Maybe this project was good when it started ten years ago, but now there are other good open source alternatives, i think the open source community should emprove these.

  60. joshmilane Says:

    This (and all competition) is good for MSFT. The Open Source community has forced them to think differently about their products and business model.

    Support Open Source! Even if you are using MS Office to do it.:)


  61. drlewis Says:

    Why? Why not?

    I prefer GNU/Linux to Windows, but as of now there are tons of Windows only programs that are nice to keep around, many of which do not run well under Wine.

    Also, it would be nice for programmers, as it would assist us in writing a Windows version of our program(s) without needing to buy Windows, or telling users they need Cygwin.

    Sure, patent threats are a concern, but preventing that FUD from allowing the free software world from giving it a shot is the same as letting M$ win.

    Realistically though, Windows still has major advantages over ReactOS and will for a long time, those advantages may not be enough to sway a free software nut such as myself, but a normal user yes. Windows comes with most computers. This is the main reason Windows and MS-DOS are/were so popular. The typical human being (trust me, I used to be one) does not have the computer skills to install their own operating system. Whatever came with their computer will be what they use. Windows also has the advantage of offering customer support and warranties, something lacking from _most_ free software such as GNU/Linux and ReactOS.

    ReactOS will only surpass Windows when the manufacturers start selling their computers with ReactOS instead of Windows. ReactOS has not proven itself yet, and is not ready to prove itself yet. It took years before GNU/Linux was finally offered by a major manufacturer, I would expect the same for ReactOS. At that point those manufacturers may offer support for ReactOS, taking away another Windows advantage.

    This is of course assuming ReactOS will eventually become as stable and secure as Windows. (Then again, that’s not saying too much. =P )

    I know there will be a market for something like ReactOS. Windows Vista may seem to be doing okay from the numbers, but many people, even many people I know myself, have decided not to go with Windows Vista. Instability is one reason, which may come and go with various versions of Windows. Price is another, not everyone buys a new computer every year with Windows preinstalled, in my household we run seven computers, we can not afford to upgrade all of them, hardware or software wise. The cost of (legally) upgrading them to Vista would be enormous. Plus, the hardware requirements of Vista make it so that only two or three could even run it, but most could run an XP-equivalent like ReactOS. Due to the nature of free software, it may even be more resource efficient than Windows. DRM is another oft-heard reason, it will probably plague Windows to the end of its days.

    There is a market for it. It can be done. Patent threats so far have all been FUD. Why not do it?

  62. jericho Says:

    This is good news for all of us! A free and open source operating system for the masses. If everything goes well and ReactOS can really compete with Microsoft in terms of performance and stability then I would not even hesitate to support and even donate a small amount for the improvement of this project. Kudos to those who are behind this project! I personally will support this.

  63. illicotravel Says:

    Make Java work on it and you’ll suddenly have many new softwares running.
    But I know that’s not the point, I can already do that on Linux.

  64. J Says:

    Microsoft can’t sue because the whole OS is being re-written; simple compatibility with Windows didn’t make Windows sue OpenOffice or Wine. I have to agree, the start menu and GUI should be redesigned to look a little less like Win 95 while still being usable for Windows users, like except it can’t support that kind of stuff for a while.

    I think the first usable version (.5 beta) is scheduled to be out about 2007/08, and I hope it makes it! Microsoft has been owning the market too long!

  65. MaxSpeederIAM Says:

    A great read, very informative
    Been looking for a blog like this one for a while
    Keep up the good work.

  66. Amado Says:

    Pretty Interesting.

  67. P812 » React OS:Here comes the Windows Nemesis! Says:

    […] Port over your favorite Linux one or write it from scratch. Lets see you do that one MS more | digg […]

  68. ynot_vs_tony Says:

    I think this is a great effort! I can even port this into my xbox, i can have a live cd for my pc repairs… There is no way you can achieve that with windows without using them on top of linux… ROS will be able to run almost everywhere. Imagine the endless possibilities of an open os based on windows running without bugs and viruses!
    Although breaking the Microsoft monopoly is a far horizon, every chance is welcome..
    You people here just ask why again and again ignoring the answers to it.. Maybe it’s just that most of you favor Linux where you see them fail to stand up against windows and make a change to a better and maybe an open source OS.
    Even MacOS is doing better Nowadays!

    I wish luck to those guys! There is a lot of work to be done though!

  69. ricktec86 Says:

    thanks a lot !

  70. react os Says:

    […] Shots: Click Here … react OS? MMM new for me&8230 looks interesting, im begin downloading… Beat Windows? VARs React to Our Products of the Year – Channel InsiderFord points out that […]

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