Hi guys thanks for the replies i flashed the BIOS to the one dated 21/01/08 still no joy locked up after a few hours on Crysis.
I have looked at the Northbridge and there is a very weedy looking fan on the heat sink there, facing down away from the CPU HSF.
I have run this system on clocked values and overclocked and it makes no difference.
I made sure all shadowing in the BIOS was turned off as well, again no difference.
Also tried the Microsoft "Virtual Address Space Fix", and installed SP1 for Vista.
I think that this combination of Hardware simply does not work, and have strong negative feelings towards Nvidia over this 680i motherboard. I found another post where someone else binned there's.
I have a graphically inferior PS3 and i hate gamepads on FPS games, but I'm still considering giving up and getting a (desktop replacement) laptop now, and never attempting to PC game again, which is a shame as i have been until the last year (when i bought this PC) been playing PC games since Doom.
I think Nvidia owe the gaming community an apology for producing such a bad product in the 680i, its the cost to my happiness that bothers me.
I will continue to search for answers for the next couple of weeks then its the scrap heap for this PC.