Your going to have to provide more details.
Whats the rest of your rig components
How long have you run the rig with the 8800 ?
Did you change or upgrade anything else when you installed the card ?
Microsoft Windows XP (Home edition SP3)
Intel® Core™2 Quad CPU
Q6600 @ 2.40 GHz
3.25 GB of ram.
Mother board is p5k
PSU: Cooler Master 750W GX
I changed the PSU as well to the 750W GX from an old cooler master 600W.
I changed the psu after having upgraded my video card. It was causing problems, but this time my screen would get white squares and random lines (artifacts? or something like that), as well as the black screen and restarts.
So I went to the shop, the guy noticed my 600W psu fan wasn't working so I bought the 750W.
I've had this PC for more then 2 years, It never had a problem. It Ran fine with my old 8800 GT, never had any restarts like this.
Benski you mean the powercord that connects to an outlet and the back of my PC?
In that case, no I am still using my old one. Something just hit me... could it be as simple as a cable problem