TF2 and L4D keep crashing my system

Been playing TF2 and L4D for months without any problems untill after my summer holiday, after i returned home in august I was not able to play TF2 or L4D anymore because it keeps crashing my pc every second, it just restarts my pc because iI have BSOD turned of. Sometimes they crash in menu and other times after 10/15 mins, it is not an overheating issue because ive been monitoring the temperatures, I thought it was a problem with full hardware acceleration but ive tried putting it back to basic but that didnt help either, ive updated my gfx drivers but thats didnt solve anythign either, even rolling back to an older driver did not work. So im clueless and desperately need help, I really hope someone can help me here.

heres a link to my minidump file, dont know if it helps
http://kiss-army-fleeto.com/Mini092109-01.rar

and a link to DxDiag txt:
http://kiss-army-fleeto.com/DxDiag.txt

(its on my private webspace, no virus, I scanned it just before they were uploaded)

Any other games you're having problems with?
That could help determine the nature of your problem: software/system/hardware

no problems with any other games, been playing games like batman arkham asylum and having no problems with that at all, can play it for hours without any crashes
it only seems to happen with L4D and TF2 havent tried any other valve games yet because it is driving me nuts already

have you tried verifying the game cache. 

Yep tried that too, didnt help at all sadly