pc auto restart issue while playing games

[james133]

hi so here's the problem i start playing the game and either at the end of a cinematic or at explosions or simlar tings happen in game, the screen goes black "no blue screen" and a few secs later i get my bios loading screen.

im very sure it's a hardware issue, have reinstalled windows many times
i just need to know what i need to replace
moneys tight don't want to wast money getting parts i don't need
id like to know what tests i should run to diagnose the issue

so this only happens in some games for example
Bioshock 2 Sniper Ghost Warrior Shellshock 2
Battlefield Bad Company 2 Borderlands and more,
but there are lots of games this doesn't happen in

System specs
xp
cpu intel core 2 quad q6600
graphics nvidia geforce gxt 260
ram corsair dominator 2x2gb ddr2
mobo gigabyte ep45-ds3
psu ezcool 700w
and no i haven't over clocked anything

i have had this problem for a good few months now
and i cant put up with it anymore
any help will be much appreciated

 

[MindoverMaster]

What are your temperatures when playing these games? Get and post a screen shot of HWMonitor.

 

[james133]

What are your temperatures when playing these games? Get and post a screen shot of HWMonitor.

when idle http://oi53.tinypic.com/11tbcd2.jpg

while playing http://oi53.tinypic.com/332v7df.jpg

 

[Zindel]

Turn down your settings on the games. Sometimes the auto detect is not the best.