Microsoft's Singularity operating system is now open to the public for download, under a Microsoft academic, non-commercial license. Inside is a fully compilable and bootable version of what could be the basis for the future of Windows, or maybe simply an experiment to demonstrate .NET's capabilities. Singularity, if you'll recall, has gained wide interest from researchers and users alike, by claiming to be a fully managed code kernel (with managed code drivers and applications as well), something that would finally revolutionize the operating system research arena. The
project is available on CodePlex.

http://www.codeplex.com/singularity