MinWin is the code name for the core components of the Windows operating system. MinWin runs the kernel, the TCP/IP stack and basic system services; it is self-contained and has no understanding of, or dependence upon, the rest of the Windows operating system.
MinWin grew out of project at Microsoft to map all the interdependencies in the Windows operating system (OS). Once the interdependencies were determined, the architects were able to break the OS down into modular parts, called layers. The bottom layer, which provides the foundation upon which the rest of Windows is built, was isolated and given the name MinWin.
Microsoft says it has no plans at this time to turn MinWin into a product. It will be used internally to allow Microsoft developers to grow the Windows operating system in new ways without having to rewrite core services or worry about breaking dependencies. The current version of MinWin takes up 25MB of disk space and can run on as little as 40MB of RAM. Future versions are expected to require less space and memory.