[HELP] computer crashes while gaming

[invisions]

Hello,

Recently my computer started crashing while playing high-end computer games(bc2,mw2 sofort) it might play for a couple hours straight with no problems and sometimes it might not even last for 15 minutes without crashing
I have tried everything i could think off to resolve this problem and sofar all of them have failed:

1. thought it might be a virus, scanned every bit with 4 different anti-virussus and malware scanners.
2. i have properly installed all the drivers.
3. i clean my computer atleast once a week so i figured dust could be the least of my problems.
4. checked if all the cables were connected.
5. removed the sidelid to see if it would make a difference (it did make a difference but eventually it still crashed)
6. then i went to the weakspot in my system the cpu cooler which was a stock amd cooler and replaced it with a mugen 2.

I couldn't think of anything else i could do to fix this issue, there for i'm asking: what could i do to stop my computer from crashing while playing games.
Could it also crash because the heat of the graphics card goes into the heatsink that lies directly under the card? (see picture: http://forums.legitreviews.com/images/random/abit_AX78_motherboard.jpg)

my computer specs:
Processor: AMD Phenom(tm) 9850 Quad-Core Processor, 2.5GHz (with a mugen 2 cooler)
Memory: 2048MB RAM
Hard Drive: 250gb
Video Card: NVIDIA GeForce EVGA GTX 285-oc
Sound Card: Realtek HD Audio output
Operating System: Windows XP Professional (5.1, Build 2600) Service Pack 2 (2600.xpsp_sp2_rtm.040803-2158)
Motherboard: abit am2+ ax78
Computer Case: antec three hundred + 3 case fans (5 intotal)
PSU: MS-Tech N750-VAL | 750 Watt ATX PSU

temperatures:
GPU never exceeds 65 degrees
CPU never exceeds 65 degrees
temperature inside the case never exceeds 50 degrees
PSU temperature unknown (but could it seriously brake down after 4/5 months of service while being properly maintained?)

 

[etk]

Most no-name 750 W PSU's just don't put out anywhere near there rated power. Seasonic, Corsair, and Antec (Less so) are all quality PSU's.

Your temps are fine

Try down-clocking your video card and CPU, they will draw less power. If that prevents the issue, you can be fairly certain it's a power limitation.

Don't be mad if your PSU shuts down, it does that to prevent it from frying your system. Many cheap PSU's arn't that courtious.

 

[invisions]

ok i turned down clocked the video card and it doesn't crash anymore, the problem with this PSU is that i got it from an RMA because my otherone did fry and burned the GPU with it.

i'll contact the store i got the PSU from asap and thanks for your help