Freeze-up and restarting in games :(

Question

Hi guys. I've been checking out these forums for a while since I've got the MSI 975x Platinum Powerup Ed. mobo, and you all seem very helpful so I decided to ask for some help
I've just bought a new comp and it's been up and kicking for a couple of days now.
However, I'm experiencing some very irritating freeze ups while playing games or during benchmarks. After half a minute of a freeze up the comp resets itself.
When i then enter Windows again it tells me that there is something wrong with my graphics card driver, and that i should check for new updates.
These freezeups happen every now and then, several times a day.
I also get random artifacts in certain tests in 3Dmark 2003, which really should not happen with this computer i guess.
So far I've tried out both the newest supported drivers and a beta driver, without luck.
At the moment I'm using a 4 pin "Pentium 4" power cord to supply my CPU with power, instead of an 8 pin.
I've been checking around on other forums, and so far it seems like that makes no difference.
All my hardware is unclocked.
If anyone have some tips or tricks to help me solve my problem I'd love it if you could share them with me 
Speccs:
Intel Core 2 Duo E6600
MSI 975X Platinum Powerup Edition
XFX Geforce 7900 GT
OCZ DDR2 2x 1GB Platinum XTC PC2-6400
Hiper R 580W

Answer 1

Ok, I've played alot of games the last days, and it's a long time ago since i got a freeze up in there. It seems more and more to be a 3dmark 2003 problem, as it almost always freezes up at the exact same moment in the same test every time. I also only get artifacts in 3dmark 03, while I've never gotten it in 3dmark 05 and 06.
I've underclocked a bit now, and I still get tons of artifacts in 3dmark 03, but atleast it suvived through the moment it normally hangs on.
There is also another strange thing that happens between the tests in 3dmark03 and when all the tests are done. The monitor keeps "turning itself on and off" constantly, as if it cant find a signal. This happens untill the next test starts when it stops. If i then exit 3dmark 03 by pushing the escape button, I get a black screen and have to restart the comp.
Sometimes I get a bluescreen after a freezeup in 3dmark 03 with a message that reads like this translated by myself:
There seems to be a problem with nv4_disp.
The unit driver is stuck in an unending loop (?). This normally means that there are problems with the unit itself or with the unit driver which programs the hardware wrong.
Quote
There seems to be a problem with nv4_disp.
The unit driver is stuck in an unending loop (?). This normally means that there are problems with the unit itself or with the unit driver which programs the hardware wrong.
After i underclocked a bit, and restarted the comp after another failed 3dmark 03, I can't clock at all anymore. I'm not even allowed to put the GPU back to its standard clock ratings in RivaTuner.
Thank you for you're help guys