On some very specific games (and I mean very specific) so that already rules out any hardware problems - my computer does a hard restart a few minutes into it. Some of the games I can't play are Empire Total War and Cold Waters - most games are fine to play. I checked my Windows error log and just before the crash it says "hardlock.sys failed to load: Driver has been blocked from loading."
I've tried many things, uninstalling drivers, running a repair on Windows with the disc, etc.
Has anyone got an idea of what this could be?