When you run up a Microsoft Virtual PC chances are you are going to want to copy files from the host system on which the Virtual PC is running to the actual Virtual PC. This is possible by simply going into the settings for that Virtual PC and selecting the Shared Folders option as shown below:
If you then select the Shared Folder button over on the right you are able to select a local directory which can be mapped a drive letter on the Virtual PC. Perfect for copying files up and down.
It is not possible to use this option to connect a Virtual PC drive to a network mapped drive you may have on the local machine. It only works with drives that are local to the host machine on which Virtual PC is running.