1. Indeed, the power supply is a good possibility.. Swap in another power supply and see how it goes..
2. Running games at higher temps that normal are not good on a motherboard.. (40 -50 C is fairly warm for a CPU.) Open up the case and look at the capacitors for any leaking or swollen parts.. Bad caps are frequently a cause of the symptoms you're seeing.
Hope this helps.
(on windows 7 (x64)
i bought my computer on sep 23, 2007 and have been playing the same games i am trying to play now with no problems at all.
But for the past 2 weeks my computer has been shutting off when starting up graphics intensive games, no BSOD, so i turned off Automatic restart in the Advanced Startup and Recovery settings to see if the bsod was showing up, but i was just missing it. Nope, the computer just turned right off, as if someone pulled the power plug. I set automatic restart on power failure to ON in my BIOS to see what would happen. Again my computer just shut off and stayed off. To turn the computer back on all i have to do is press the power button, no unplugging or resetting.
The graphics card i am using is a
Nvidia Geforce 8800 GTS 320MB (see other system specs below)
I have installed it in a separate computer with a 375w power supply, dual core processor, and 3 gigs of ram and can run these games with no problem, so either the card is okay, or this system cant push the GPU enough for it to fail because of small PSU, etc.
Back to my original computer. It does not shut off if i start my games on low settings, then in-game i set them higher, however if i set them too high my computer will still shut off.
I have placed an older card, a Nvidia Geforce 7900 GS in the system and can run the same games I'm trying to play on the 8800, on any graphics setting, without my system shutting off. I'm assuming because it is much less power hungry.
I think it is the PSU because I'm not getting any errors at all, not even in the system log. Its not an overheating problem as i keep the computer dust free, and have recently changed the thermal compound on the GPU and CPU with non-conductive thermal compound. And i can run games forever with no overheating issues, my CPU temp will sit at 40