Try resetting the CMOS. Turn off the PC, unplug it from the wall and look for a jumper on the motherboard marked CMOS. You will either move the jumper from the 1/2 pins to the 2/3 pins or just remove it completely according to your motherboard instructions. If there is no jumper, remove the CMOS battery fro at least 30 seconds. Replace the battery or put the jumper back into it's original position, plug the PSU back into the wall and boot it up. You should then be able to load defaults and be up and running.