I overclocked my GPU core from 450Mhz OC'd to 527MHz and memory from 532MHz OC'd to 637MHz. now when I try to raise it up it fails the required test inorder to use the new settings. I think this is because I need to raise the voltage, now I've been looking around and found nothing about raising the voltage of the GPU. My card is a Geforce 6600OC 512MB PCI-E. Any one know how to do this?