A colleague passed me a Virtual PC machine that consists of two files, a .vmc and a .vhd, where shall I put them, directly in the "My Virtual Machines" folder, or is there another location?
Are you running Windows 7? If so then you can mount the VHD directly from Disk Management. I think it's in the Action menu.
As for where to place the VHD, it doesn't really matter. The VHD is the actual disk and the VMC file is the configuration file. Just make sure that they are in the same folder.