try setting the bios back to basic. Open the case and remove the battery from the motherboard. Find the bios reset jumper this is normally set to bridge 1 and 2 for normal use and 2 and 3 to clear the bios. This is done with the pc disconnected from the supply. After about 30 seconds set the jumper back to its original position. If you have the motherboard manual this will be indicated. If not just a close look at the motherboard with a torch should find it.