I hope reverting a system to Windows 7 from Windows 8 or 8.1 doesn't require the Retail copy of Windows 7. Could I install an OEM version or is the motherboard binded to Windows 8? The retail copies of 7 are expensive and rare. BTW, my brother is looking to buy a Dell Opteron to present his thesis. He doesn't want to use Windows 8 or 8.1. I hope all is not lost.