Actually, Microsoft is seriously developing a version of Windows Server that will be aimed at grid computing. It's called ... wait for it ... "Windows Server 2003, Compute Cluster Edition" -- I like my version better ("Windows Server Grid Edition"). Anyway, here is the lowdown on that.
I wonder if this means that Google is thinking about converting its notoriously-rumored grid cluster of a half-a-gazillion Linux boxes? Probably not.