The ReactOS® project is a ground-up implementation of a Microsoft Windows® XP/2003 compatible operating system. ReactOS aims to achieve complete binary compatibility with both applications and device drivers meant for NT and XP operating systems, by using a similar architecture and providing a complete and equivalent public interface.
Written completely from scratch, ReactOS is not a Linux based system, and shares none of the UNIX architecture.
The main goal of the ReactOS project is to provide an operating system which is binary compatible with Windows. This will allow your Windows® applications and drivers to run as they would on your Windows system.