When we're talking about M$, have anyone tried
http://www.reactos.com/ ?
It looks very interesting.
"The ReactOShahaha174; project is dedicated to making Free Software available to everyone by providing a ground-up implementation of a Microsoft Windowshahaha174; XP 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."
Too bad it's just in a BETA stage.