Ah never mind then. I misread what you wrote and thought both versions were running the OEM installed copy.

It won't like you doing that and will want to reactivate the MSDN version at least.

The OEM BIOS activation works by having a digital certificate inside the actual BIOS that has a corresponding serial number. If the certificate doesn't match the keyed in number then it will complain at you and want to reactivate. If it does still match then it'll assume that you're running on a licensed Vista machine.