As I've said before, your not aloud to use windows within a virtual or otherwise emulated environment, that's because your suppose to buy a separate copy of windows for each machine instead of being able to having a possibly portable version, also Microsoft want windows to have direct access to your hardware without restriction
With Ultimate/Enterprise/2008 you are aloud to to use it within a virtual environment. It works for me with ultimate, pretty well with 7 and xp but I believe that Windows Virtual PC is telling the virtual machine stuff about hardware

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