Virtual PC
Here are some interesting blogs that are dedicated to Virtual PC
There are some fundamental features in Virtual PC that you really have to look at. For example differencing disks, see HOWTO: Use Virtual PC's Differencing Disks to your Advantage and you can also compress your VHD files, see Compact Your VHD Files.
Tip
On several keyboard layouts and for example on a AZERTY belgian keyboard you need the Alt Gr key for the backslash square brackets, etc. Inside Virtual PC the AltGr key doesn't work, therefore you can use an alternative for the AltGr key, which is Ctrl+Alt.
Update
There is a hotfix now for the AltGr problem.