This is interesting... so can this be done on an external hard drive? If so, any idea how the boot manager will react if the external drive isn't online at next boot? Ideally it would ignore the option (much like VPC). Worst case it would hang the boot...
Also, I'm assuming it wouldn't be a good idea to run this same VHD from a boot prompt as well as VPC? My guess is that the drivers would need to be different...