I actually let Windows 10 install, then found 90% of my games (admittedly old ones) simply refused to work. So I wiped and reinstalled Windows 7, did the whole windows update thing, then went to bed. Woke up the following morning to find Windows Update about to reinstall Windows 10. So glad I woke up when I did.
Installed GWXControlPanel almost immediately after that. Just checked, and it appears GWXControlPanel makes all the necessary adjustments to registry for me.