System freezing with new graphics card

[Egan]

Hey all, wonder if any of you can help...I recently bought Colin McRae DiRT for my PC and realised when I got home that the minimum requirement for the graphics card was not fulfilled...and I'd been wanting to upgrade for some time so this was a perfect excuse

So .. I've upgraded from a BFG 256MB GeForce 5500FX to a Sparkle 512MB GeForce 7600GS.

However, my computer has started to crash in the forms of freezes and blue screens of death.

When running nTune's stability test on its lowest settings it makes it two or three animations in then freezes...I did briefly think it may have been an issue with power supply (says minimum of 300W and I have a 300W supply) so I unplugged my cathodes and second hard disk and CD drive etc and ran it again...it got a bit further through the test (like 4 animations rather than 3) then did the same thing...I don't know if this is just a fluke or whether I am really low on power for it.

Suffice it to say I don't want to splash out on a new PSU if it isn't the cause of the problem! So any advice would be greatly appreciated.

Also, Battlefield 2142 which worked on medium graphics with the 5500 is now freezing on the options menu with the 7600! All the minimum requirements for the games and the hardware are fulfilled and in most cases exceeded so I don't know what to do

Setup:

Gigabyte GA-K8NSC-939 MOBO
Sparkle 512MB GeForce 7600GS GPU
Creative Sound Blaster X-Fi XTremeGamer Sound Card
Athlon 3700+ running at 2.85GHz stable (tried factory settings and is exactly the same)
Western Digital 80GB IDE Hard Disk (is the lack of SATA a problem in this age?)

My system is now idling on 23 degrees C so I doubt it's a CPU overheat issue...

Looking forward to hearing your suggestions

EDIT:
Drivers are as up to date as can be and I tried using 3DMark03 and the first test didn't get very far at all (had a FPS of only around 150fps which according to my friend is slow for that test - he only has a GeForce 7800 so it shouldn't be massively different!) and then froze

 

[MoD_Callidus]

obvious out of the way first, have you removed the drivers fully, and we do mean FULLY ? lol try using cccleaner or drivercleaner then reinstall a fresh set and post back

 

[Egan]

Used drivercleaner and installed the latest drivers from the nVidia website and it's exactly the same...though I notice it also gets a little further when I remove my overclock...which I would assume uses less power...is it likely a lack of power would cause these sorts of problems?

The nTune Stability test seems to be showing progressively more advanced animations which again I would assume requires more power, so it would make sense that if it's on the borderline of running out of power, removing an overclock would mean it has just that little bit more to get to the next animation before disappearing again...I don't know though, never had this problem with a GPU before =S

 

[rounddodger]

Yeah I recently chucked a 7600GT into my girlfriends crappy old Dell (which also has 300W) and it worked perfect, even overclocked it a bit an all.

It's only powering a stock P4-3Ghz and 250GB SATA with a DVD-RW at the moment though.

 

[Egan]

I decided to try a system format, for a while it worked great but now it's started to do it again...I used system restore to remove the windows updates I made between it working and not working but no luck...it would suggest to me that the card is at fault?!