> Doesn't M$ own 51% of Apple?

They sold that a while ago, for a nice profit. MS bought Apple shares and kept them for 5 years as was required by the agreement but that's it.

> Mac OS on the Xbox 2 PC?

I really doubt it. It's not part of MS's vision, when have they not been in complete control of whatever they were doing, especially including the OS? And for that reason, they won't port .NET to OS X either.