He is breaking the EULA. he is upgrading, not replacing due to motherboard malfunction.
To be within the EULA and if you're changing hardware. You must meet the following criteria:
-Must use the same case the OEM COA sticker is attached to.
-You can only replace the board if it is faulty, not if you're upgrading.
If you meet both, then you are within the EULA boundaries. If only one, then you're breaking it.
What the OP is doing is in gray area. so as long as he knows what he's doing, MS is none the wiser.
also, going from that p5ql-vm to that p5q pro is no major change. They are the same chipset, although the 'pro' version might have onboard RAID, so it uses a different southbridge. So as long as the OS is originally installed using basic ATA drivers with no AHCI or RAID, then the OS should come up without a problem.