As a general rule, I take it I shouldn't mix and match: professional, enterprise, retail, oem, msdn, ... ISO and their respective activate KEYS?
Here's the problem: I recently got a new computer with windows 8.1 OEM installed. While during install setup of a Hyper-V VM, I used the same disc and key that came with the machine (because it didn't accept the MSDN key). After a few days, the VM started to complain. Since the VM is for testing, I tried to re-activate by entering my MSDN key again (gotten from my subscription) but it still doesn't work.
I have done considerable configuration to the VM, and don't want to loose it, just want to activate it.