CMOS Settings for PNY GeForce 8600 GT

One question, why do you want to change the voltage of the PCI express, have you by any chance overclocked your machine? If not the default values should do fine since the 8600GT is not a power hog.

If you have overclocked then the recommendation is that you try to see if you set the PCI frequency to 100 (default) so that the PCI-e bus does not get overclocked, as its known that some devices fail when the bus is increased (such as the SATA hard disks, etc).

You will also not have to change the voltage of the PCI-E bus unless you have aggressively overclocked your machine.