Hi, i am changing the motherboard on this computer of mine as one of the RAM slots and a PCI-E slot have stopped working. I have OEM version of Win 7 which i upgraded to Win 10 on this. I had also created a USB media for Win 10. Looking at some of the forums, i can see that some people say that the COA key is somehow in the BIOS and when doing a clean install it shouldn't ask for a COA key. My issue is i am changing the motherboard. Should i be installing a clean install from USB or should i try to install Win 7 and then wait for the upgrade message and then do it that way. Just not sure if this will cause some problems with my OEM key.