Before I continue, my specs:

AMD 64 3000+
1.5GB DDR RAM (about 366mhz on two sticks, 200mhz on one, all single channel)
NVIDIA GeForce 7800GS (AGP 8x), OCed by XFX and fitted with a custom XFX fan as well.
500mhz PSU
Motherboard is a Socket 939... I think. Either that or a 754.

And yes, I am using the latest driver from NVIDIA (93.71). All right, I've got an interesting one for you. I'm fairly certain this is a graphics card related issue. Basically I've been suffering random crashes when playing games for a few months now. The crashes never happen outside of games. It all started with a demo of Call of Juarez. At random points during play, my computer screen would switch into standby mode and fans inside my computer would speed up (or at least sound like they were). I assumed this was some random software fault and reinstalled the game... surely enough it crashed less often, if at all after that, so I thought I was fine.

After that, I bought Gothic 3, and the crashing started there too. So, I reinstalled it, everything was fine, but then it happened again (seemingly when I didn't go into the menu and save for a while... which would allow my GPU to cool down, I suppose). Then it started happening recently on The Elder Scrolls IV: Oblivion. And again on Warhammer 40,000: Dark Crusade. I've ran a temp check, and with Oblivion the crashes appeared to correspond with higher temperatures, as I was running at almost 70C when it crashed. But then I tried the same activity in the game again, and it went up to 73C with no crash. And the most recent Dark Crusade crash happened at only 59C. And my card's cooldown threshold is at 115C so it shouldn't happen anyway. Though the temperatures are unusual, as before it always held at about 45-50C, even when gaming.

Another strange thing that happens is that after each crash, it can be difficult to get my computer to boot up again. All the fans and such seem to turn on just fine, but the monitor never comes out of standby (even if I turn it off and back on again) and there's no beep like I normally get to confirm it's loading the BIOS. I sometimes have to try several times, or leave it for anything up to an hour before trying again, and then it boots up just fine, and behaves as normal... until the next crash.

Crashes and hightened temperatures have continued to happen despite thoroughly cleaning out my graphics card fan and cleaning off the graphics card surface as well, *and* making sure the power cable is dust free, properly connected, and has no bent pins. I don't think it's a driver related issue as this was already happening prior to my card's last driver update, I think. I've even checked my CPU temperatures (50C maximum) and PSU voltages with SpeedFan, and they seem to be well within tolerance.

Whew, I think that's everything. I'm not a complete computer dunce but I'm no expert either, and this is starting to stump me. Can a wise guru please offer me some assistance? ^^