Moving to another testing environment

As XP screwed up itself again I decided to remove it and install Vista in the VM instead.
So now grover and I will be able to compare MOSA's behaviour on XP and Vista.
Shouldn't make any difference at all, since we're not relying on the system underneath (apart from having to use Visual Studio for development).

Furthermore I'll now be able to use Pex (unfortunately there's no version for XP availabe) to generate some more random testcases for MOSA.