Lately I have been getting random reboots during games. I'll be playing, and the next second I'll be looking at the POST screen. Is it possible that the video card is overheating? Could that trigger a reboot? Could it be the power supply? It happened after I cleaned out all the dust in the case as well, so I don't think its that. Any help would be greatly appreciated.

Oh yeah, I forgot to mention, my video card is a G-Force FX 5950 Ultra Golden Sample card, and it seems to mostly only freeze on RTS games, like C&C Generals and LOTR: Battle for Middle Earth.

I have had this problem many of times with people who build their own computers. first thing first --> search on google for memtest86 and put that on a bootable floppy and let it run overnight ( test one stick of memory at a time ). if you get any errors replace the corrupt stick of ram. Next make sure your heatsink is adequate and check your temperature. the CPU temp generally should idle in the 40's - 50's and when playing a game should not go above 65 (all in celsius) - take off the side panel and point a desk fan blowing at the cpu. I dont think a video card overheating would trigger a reboot - the game would most likely just slow down. it sounds like your processor is overheating because the games you mentioned load the cpu up pretty good. last thing you could buy a new power supply. Allied has a great 400w PSU for 35 bucks. Antec makes great cases too. try a different video card as well - reinstall video drivers www.nvidia.com - good luck and let me know how it works out.