Having installed a new motherboard here and there and aware that an existing system will not run- so wound up having to reformat reintroduce the operating system system so to speak and get validation from MS All of that I am aware of. Now here is a new problem looming. This PC is a preloaded OEM system - No operating system disk.but possibly a back up/rescue disk[ don't know yet what I am going to be given] How does one get the fully loaded hard drive to speak to the motherboard[ or is it the other way?] so that at least validation[if needed] can be achieved. This is project on the horizon. I been asked can do?
the motherboard is not twinned with hard drive > tattooed < and the motherboard chip sets are similar, you might get away with a straight swap.
If the motherboard IS twinned to the hard drive and you have a 25 digit product code. You could wipe the hard drive, destroy the mbr ( remove partition ) and install from a full copy of the O\S. You then put in the OEM code number and ring M\S and explain the motherboard has gone. Most times they are fairly good and will re-activate the O\S.