Get a PSU tester, preferably one with a LCD read-out, 12 bucks on ebay, and find out if the PSU is receiving enough power on all the rails. Unseat and reseat the RAM. Do a full dust-out, and check the CPU as well. Unseat and reseat the video card. After all that, reset the board by the CMOS jumpers and unseat and reseat the BIOS battery.