I think most of you are missing the point. As I read your suggestions (except maybe for one that suggested rewriting from scratch), the expression "polishing the turd" comes to mind. If Microsoft doesn't rewrite the whole thing and gets rid of all the compatibility crud (perhaps by virtualising it), Windows is doomed. Think about it: Vista code base is 40% bigger that XP code base (an unconfirmed quote from somewhere online) -- there is no way you can turn this to an advantage! There is a good article somewhere on the nets comparing Vista to dBASE IV (hint: compatibility killed it). The problem is, though, that at the moment compatibility is all that Windows has. If people had to choose between, say,  Windows-2010-Without-Backward-Compatibility and other OS, they'd probably keep running XP forever (in enterprise) or switch to Mac or Linux (at home). Make your own conclusions.