Question : windows xp mode not mounting vhd drives created in Virtual PC 2007

I have about 8 different virtual hard drives that were working just fine in Virtual PC 2007 under Windows XP x64, 4 XP SP3 machines & 4 W2K machines.
I recently installed Windows7 Ultimate to the same computer.
I installed Windows XP Mode (and the updates) and can open a newly created XP machine just fine.
However, I cannot mount ANY of the other virtual machines even if I delete the VMC file, create a new one and attach the VHD file.
I get the following error " 'xxxx' was unable to write to one of its virtual hard disks. " after creating a new machine (all of them give the same error!)
If I try to load the original VMC , I get the following error "The virtual machine could not be started. An unknown error occurred."

I checked security settings, but no luck there either (tried taking "ownership" as well with no luck)

Any ideas?
There is quite a bit of data on these I'd hate to lose.

Answer : windows xp mode not mounting vhd drives created in Virtual PC 2007

Do you have UAC on? If so, can you turn it off and try it again?