Problem with XpertVision 7600GT

Let me begin by saying that im new to these forums and they were suggested by a friend for solving the problem iam currently having with my computer.

Let me explain, Last week my Nvidia 7600GT card suddenly stopped working and i was forced to use my onboard video. So after testing the card on another computer and trying various things i came to the conclusion the card was broken. It was working fine until then and all of a sudden stopped working, but such is life so i decide to buy a new card......

I looked about on the net and saw that the XpertVision 7600GT seemed a good buy and proceeded to buy this card as a replacement. Ok so i get the card and plug it in, everything seems to be working fine, installed the drivers, everything is normal. So i decide to test the card before i start overclocking or anything run 3dmark03 so i can see a benchmark in performance for the future as you do.

Now when running this program i got the the 4th game "mother nature" and almost immediately my system turned off. So i turn it back on and notice that my monitor is giving me the message "no signal". So i turned the lot off at the wall socket and turned it back on again and. Now it worked again as before, very strange...

I decide not to run 3dmark03 again after this and run Medievil 2 TW instead and max everything out on it. This works ok for about an hour then the same crash happens!

Now i run medievil 2 TW again to make sure its not a 1 off random crash, after about 15 minutes i discover that it is not. So i run speedfan and check my 12v 5v and 3v rails everything seems normal.

Next i open up my pc and check all the fans are working and clean and reseat the graphics card.

Then i check the temperature of the card and make a log using speedfan and run 3dmark06 (Not 3dmark03) this time 3dmark06 reaches completion and all temperatures are well within tolerances according the the logfile, the temperature of the card actually remained at a steady 39 degrees celcius throughout.

Now i re run 3dmark03 and the crash happens again at the same point. I do it twice more and twice more it crashes. I feel i should also mention this never happened with my old Nvidia 7600GT. Only when using the XpertVision edition of the card.

Now im starting to think thats its a software problem so i download every single windows update and run virus checker , spyware scanner and run direct x tests. Everything checks out..

So i re-run 3dmark03 and get the same crash at the same time after all this.

Next i double check my PSU but it seems fine on all rails.

Still getting the same problem.

Anyone know what could cause this or had a similar problem?

My PC specs are

Athlon 3800+ X2 processor
2048MB Corsair Value Select RAM
XpertVision 7600GT 256MB GPU
ATX 400W PSU

i can find out the motherboard model aswell if that is helpful i got it written down somewhere.

also worked out that my system requires 340w power using the extreme overclocking power calculator.

Any help would be much appreciated

Regards

Necrosjef.