How do I restrict access to settings on Virtual PC 2007?

Hi,
I am trying to lock down (with a password) the .vmc file from being edited by users who will use VPC2007 on their own machines (which they have administrative privileges to).
I see i can restrict some of the options to administrators only, but its no good since, as i mentioned, the users are administrators on their own machines.
Note that the host machines will be seperate workgroup machines on the users homes.

If possible i would also like to let them choose which options they will be able to change, for example- the RAM the virtual machines will use.

Any ideas?