Getting started with ReactOS

ReactOS is a relatively new open source operating system that resembles the looks of Windows NT and aims to offer similar levels of functionality and application compatibility. Featuring a wine-based user mode, this system doesn't use any of the Unix architecture, but is a rewrite of the NT architecture from scratch, with its very own FAT32 implementation, and completely free of legal implications. That said, this is not yet another Linux distro, but a unique Windows-like system that is a part of the free software world. This quick guide aims at users who want an easy to use, open source replacement for their Windows system.

Source: Howtoforge Linux Howtos und Tutorials