In my opinion, if he’s only changing his mother board, first uninstall all motherboard / chipset drivers and let him do the swap and see if windows accepts the change without needing to be re-activated. Because it’s a combination of hardware components, not just one that windows use to generate its unique number sequence. Now, knowing windows and their stringent licensing scheme it might just ask require re-activation, in that case you’ll have to do it.
Now all you have to do is install your new drivers that came with your motherboard and your're set. Formatting is good, but is isn’t always necessary.