Hi- I have two 7900 GTs that when I run in SLI mode the screen will work fine for a minute of two then all of a sudden the screen will start flashing lines and become a garbled mess. After lots of screwing around I discovered that if I ALT-TAB the game and then bring it back it will run better for a while. But then it goes back to the same thing again or runs super slow. I've tested both cards separately and they seem to work fine. THis problem ONLY occurs during games, never on the desktop. Anyone have any ideas? TIA!

Also, even more wierd- my computer's humming sound (the fans) seem to vacilate alot and I noticed that whenever the sound seems more "bogged down" the graphics start skipping. Anyone ever heard of such a thing? Problem with the power supply or something?

What make, wattage, and amperage PSU are you using??

Hey! I'm not too good with this stuff but here's a description from the IBUYPOWER website of the PSU. Here's what is says on the PSU-
DC output +3.3v +5v +12v1 +12v2 -12v +5vsb
Max A. 34a 40a 16a 17a 0.8a 2.5a

Description:
NZXT PF-500 500 Watt Power Supply

Specification:
Type: ATX
Maximum Power: 500W
PFC: No
Power Good Signal: Not specified
Hold-up Time: Not specified
Efficiency: 70% Min. at full load
Over Voltage Protection: On all outputs
Overload Protection: On all outputs
Input Voltage: 115/230

Also, I forget to mention that the hum pitch changes everytime I move my mouse as well! thanks for your reply!

The next thing you should do is go here - http://www.extreme.outervision.com/psucalculator.jsp

Calculate how much power your PC actually needs then post the result in this thread.

I came up with 350 w according to the calculation, but I"m not sure I put all the right numbers in. My PSU has 16 amps on the 12v1 rail. Maybe that's not enough? Have you ever heard of moving a mouse changing the fan pitch? THANKS!

Most people recommend 18 amps or more on the 12 volt rail.

The only time I came across a similar problem with the noise to yours was with a crappy old Windows 98 pc that had a brand new dvd burner fitted into it. That problem was caused by the 85 watt psu the thing had in it, it was so pathetic that pressing the eject button on the dvd burner would shut the psu off.