(All the machines referred below have Windows 7 Professional.) I have a virtual machine targetted for Virtual PC. I'm able to use that disk in two different machines (32 bit and 64 bit, respectively). Yet in the machine where I wanted to finally install this virtual machine I get the error that the VHD file is not valid. The faulty machine is 32 bit and has the exact same Virtual PC version as the other machines. The file was correctly copied (SHA1sum says so). Default XP Mode works (therefore Virtual PC is not so wrong) Does anyone have any idea what might be wrong in the target machine?