I just got a 6600gt agp, and I've started having problems with artifacting, like crazy textures and polygons streching across the screen, and crashing/bsod-ing. At first I thought it was overheating, but I put on some new arctic silver and now its a little more acceptable temperature, but the artifacts are just as bad. Now I'm thinking its an inadequate power supply - I tried unplugging everything but the hard drive and video card, and it seems to improve the problem to some degree, but it just takes longer to crash. I've taken a look at the graph of voltage over time, and it seems 12v fluctuates between 12-12.4, 5v is 4.65-4.85, and 3.3v is pretty consistant. Under load, the 5v seems to be consistantly 4.65, and the 12v is about 12.4.

4.65 seems low for the 5v rail (>5% difference), could that be causing artifacts and crashing?

I have very similar issues sometimes with my 7800gt and it seems to be directly related to the ambient temperature in my room. For whatever reason my motherboard doesn't support the utilities that report the card's temperature so I can't really verify it but everything else I've witnessed seems to point to that.

yeah 4.65 on the 5V rail is pretty bad...What kind of PSU is it? Do you know if it has always been dipping that low? The 6600GT doesn't use up that much power.

Its a raidmax 350W. 350 is supposedly the minimum for the 6600gt.