ReactOS is an open source, useful operating system based on the Windows XP/2003 architecture. Beying written completely from ground up, it is intended to follow the Windows platform designed by Microsoft from the hardware level up to the application level. This is not a system based on Linux, and has nothing to do with the UNIX architecture. The main purpose of the ReactOS project is to provide a binary compatible system with MS Windows, allowing any Windows applications and drivers to run as they would on a Windows system. Additionally, ReactOS uses the look and feel of the Windows operating system, making the OS straightforward to the users accustomed to the familiar interface of Windows. The ultimate goal of ReactOS is to allow the user to replace Windows with an equally useful and user friendly OS without noticing the change.