Unstable computer with BSOD while playing game

I have a problem of instability. I recently recovered a computer with specs as below:

Intel Core 2 Duo E7200 2.53 GHz motherboard
NVIDIA 7600GS AGP port
2 GB DDR II Corsair 5300 (667 MHz)
Samsung Hard Drive 320 GB
Creative Audigy sound card LS
Windows XP Home OEM Service Pack 3.

What I initially seemed is the score I got in 3d mark 2006: 2300 points. Ok, this is not a monster performance but still! I come to have almost the same score with another computer with the same graphics card but a hard drive IDE 7200 trs min 8 MB, 1 GB DDR and a socket Celeron 478 overclocked to 3.4 GHz.

Then I saw there was a real problem playing Battlefield 2142. After 20/30 minutes of play, I have a blue screen of death that appears for less than a second and the PC restarts.

I installed the latest version of OCCT, and I launched a basic test of one hour. I get an error code 1 after 30 minutes. It seems to me that my problem could come from my PSU (with 450 Watts).

Would it be enough to properly feed my configuration? In my opinion, I think it could be the cause of the instability, but I'm not sure. I need advice on this matter. Otherwise, that may come the problems? Poor settings in the bios? Is there an downclockable processor ?

Set the default settings in your bios and try a small memtest session to begin.
And if you found any mistakes, retry the test with a single card. In fact, your memory is the classic or the high end?

Thank you very much for helping me! So I followed the instructions. BIOS settings set to default. I launched a session of memtest and found no error. Regarding memory, I think it's classic.

Increase the voltage of your memory at 1.9 volts and relaunch the tests. If you could press the buttons then PAUSE your keyboard at a Blue Screen of Death, and note the error encountered. Otherwise, open the Control Panel in XP, the administrator tools and the observe the system log to identify the type of problem (usually indicated by a white cross embedded in a bubble red).

Your score in 3DMark 2006 does not seems to be abnormal for 7600GS. However you can just overclock your graphics card if you want better scores on this bench.

I would like to draw your attention to the fact that if you like to renew your graphics card for something more powerful than the port PCI-Express cable is only 4X.