My PC crashes while playing games

[Prashanth0006]

I've a pc with the flg specs:

AMD Phenom 2 x6 1090T(3.2ghz stock speed)
Transcend 800Mhz ddr2 6GB (3 x2 GB sticks)
XFX Radeon HD 4670 1gb Graphic card
M4A78-EM/1394 motherboard
Seagate 1TB 7200RPM(primary hdd)
Seagate 2x500 gb 7200 RPM(for storing my stuff)
CM Extreme Power Plus 500W psu

I've been using this pc for past 2yrs and no problems so far. Recently, I've used the "M5A88M" Motherboard along with Frontech DDR3 1333 1x4GB RAM. The processor, graphic card, hdd and remaining components are same except the board and RAM. The build worked nicely. Now, I've reverted to my own board (M4A78----). I was playing games like NFS Hot Pursuit, Just Cause 2 and so on. After a few minutes of gameplay, the pc crashes without any error. Not even check for solution msg box, no BSOD. No events recorded in event viewer. So today, I reformatted my pc and installed windows 7 Ultimate X64. But the problem is unsolved. I've checked my hdds for bad sectors, defragmented the disks, checked for malware/viruses with kaspersky. All are working fine except the games. And also the firefox is crashing while viewing the pages with flash content.

No overheating issues and the hardware is properly fitted.Thermal paste is also fine. Checked the RAM with memtest+ for over 9hrs and found no errors.

Pls solve this problem.

Thanks in advance...

 

[Ranger12]

This is kind of a shot in the dark but if you can, try swapping out the power supply. If that doesn't work try swapping out the videocard or running it with the onboard video.

 

[Prashanth0006]

I have tried a new power supply(my another pc's) and removed the graphic card and connected monitor to my MoBo. The change was that the games run lagged(only 7-12 fps) but there was no crashes because I couldn't play the games for more than 1-2min. Now I reinstalled my g-card and run the games. They run smooth, now the pc isn't crashing but the games crash (like "xxx" has stopped working). So I thought the problem was with my drivers and I upgraded to the latest and BIOS also updated. The temperatures in gpuz are showing ~64C after I play games for 10 min. After the game crashes/closes the temps are around 35-40C. Is the GPU temp the culprit??? The processor usage is just around 30% while gaming and it's temps are normal. The processor is installed with cooler master silent heatsink and fan. The thermal paste is freshly applied.I have checked the gpu with furmark and ati tool and for the whole system I've used Hot Cpu tester pro for 6hrs and no errors are reported by them except that sometimes the ati tool shows me some yellow spots on the fur rendering window(it only happens some times).

Any solutions/suggestions??