ReactOS is built from scratch and can run Windows binary files
ReactOS, a free open source operating system based on the best design principles found in the Windows NT architecture, is now at version 0.3.15.The current version of ReactOS, 0.3.15, has been in development for over a year and it incorporates architectural enhancements for the NT architecture.
According to the developers of ReactOS, the main goal of the ReactOS project is to provide an operating system which is binary compatible with Windows.
Highlights of ReactOS 0.3.15:
• Preliminary support has been added for USB mice, keyboard, and storage devices;
• A rewritten session management subsystem has been added;
• AHCI support has been implemented with the updated UniATA driver.
A complete list of updates and new features can be found in the official announcement.
You can download this interesting operating system, ReactOS 0.3.15, from the official website.