Just started overclocking my mates old machine, P5N 32E Sli + Mobo HyperX DDR2 800Mhz @ 5-5-5-15 4GB Q6600 @3GHZ XFX 8800 Ultra. Machine overclocks fine up to 3ghz, but past that, when you boot into windows, the 8800 Ultra isn't recognised, no GPU is detected ?!?! Anyone come across this before???