Originally Posted by muzza
i have just tried updating my mobo i downloaded the xp 64bit and it says " setup has detected that the os in use is not windows xp x64 edition"
That's pretty conclusive that your os is XP x86 (32bit) wouldn't you say ???
Remove any graphics card overclocks and run 3DMark05 to see if it shows artifacts, it sounds as if your card may be overheating, when you said your temps are OK did that include the graphics card? Other than that it may be on the way out.
Have you checked that the graphics card heatsink isn't full of dust?
You'll need to remove the shroud to be sure and if it were me I'd remove the cooler and replace the thermal compound while I was in there.
If the video card memory is on the way out there's nothing you can do except RMA it (if it is still under or has lifetime warranty)