If you ever need to move a virtual machine from Virtual PC to Virtual Server, you need to uninstall the Integration Services before you attempt to connect it to Virtual Server.
Each product has their own version and they are not compatible.
Also, once the VM is up and running in Virtual Server, you can’t uninstall the Virtual PC Integration Services ( at least I’ve never been able to find a way ).
Note: There may be tools that do this, but I’m not aware of any. So if you know something I don’t please put a comment on this article.
Finally, make sure you consolidate any snapshot images and do a clean reboot and final shutdown before you begin your move.
You’ll be much happier in the long run.