First, the recommended way to create a new VM as a copy of the old or
move it to a new host machine is to do the following:
1) Shut down the VM on the existing system (don't save state).
2) Copy the virtual disk file (*.VHD) from the old to the new host PC
3) On the new host open the VPC console and "Create new" VM.
4) In the dialogue set your VM options but instead of creating a new
disk, navigate to the copied VHD disk file from the old system.
5) Start the VM from the console

Now it will boot up just as it did on your old system.

The reason not to move the VMC file is that it contains hardcoded full
path of the VHD disk file and also the VM network MAC addresses, which
should never be duplicated. By creating a new guest VPC will make sure
to generate a new unique MAC address so there will be no potential
collisions on the network if both would run simultaneously.

Concerning licensing, if you copy the VHD from your old to your new
system and create the guest as described above, then you are fine
provided that you delete the old VHD and VMC files (after verifying
that the new guest runs fine first of course).
I think you may even keep the old VHD file as a backup copy provided
you don't use it separately anywhere.

Sometimes the activation will trigger because the new VM runs in a
slightly different environment (basically a new MAC address and a new
CPU type) but that kind of reactivation is usually very simple.
The beauty of VPC guests is that they have the majority of the
hardware inside the guest exactly the same even when running on a
completely different host system so nearly nothing changes and
activation usually is not a problem.

Notice that if you are using VPC2004 on your old system and you have
VPC2007 on your new system then you should uninstall the VM Additions
from the VM before shutting it down for the copy. Then in the new
system just install VM Additions again and you will have the new
version compatible with VPC2007.

Bo Berglund