The graphics card probably didn't cause the symtoms as you suspect, but this is where the whole thing started when I first installed windows 7. So, since all other components have been replaced or removed, and tested to within an inch of their life, the only thing left is the motherboard and the CPU.
Memtest again showed no errors and WD lifeguard, running now, probably won't find anything on the new HDD. DVD drive is new and the video card is new. Only thing else is the card reader. Should make for an easy strip down.
A new mobo would just about cover the entire works. If it still has issues, then its not the computer!!
Thanks again for all your help