ReactOS is a free and open-source operating system for x86/x64 personal computers intended to be binary-compatible with computer programs and devices. Developed by Aleksey Bragin
License: Open Source
ReactOS is an open-source operating system that aims to be compatible with Windows applications, while Windows 2000 is a legacy OS that is stable but no longer supported. ReactOS offers customization and is free to use, but lacks the stability and extensive support of Windows 2000.