Right, So i've done most of the things you've suggested apart from the memtest (which i'll do a bit later) I reseated everything, and i thought for a second that maybe something (sound card which i've never reseated it) had sorted the problem as I managed to get through the entire opening cut scene of
F.E.A.R. But then a short way into the game i discovered how to slide tackle and went a bit crazy tackle bad guys and the computer restarted it self
Is there any chance that it could be the motherboard that is causing this? When I first received the board it was faulty and had to get it replaced.
I'm not really 100% sure whether the problem has always been there, this is because its only recently games have become more demanding (slide tackling) and its only really started to show through this. I never experience this problem in games like HL(1), wc3, FM2006 and other various old school games.
Im gonna try the memtest later though to see if that can give any evidence to the problem. I've done it a few times before but no longer that 3-4 hours at a time.