Virtual PC creates a universal environment for the (VM)virtual machine, which is why you have to install it before you can create VMs. You can import and export the VM from machine to machine as you want as long as you get all of the necessary files. If you forget one of the files, you are screwed. Just make sure that when you export, you grab all of the files and move them to the other machine.
I know this from experience in the virtual cloud computing data center I work at. I have people try to give me VMs to import to the data center's vSphere 4, and it wont work because the clients forgot part of the VM.
The following is information was found here doing a simple Google search.
If moving it to another PC, just copy over the .vdi file and import it using the 'Virtual Disk Manager' under the 'File' menu . Then create a new VM with the same 'hardware' settings as the original and point it to an existing disk image (the one you just copied over).