Don't know what you've done recently with your system. If you have a new cpu or ram, check the motherboard specs for compatability. New cpus sometimes require a bios version to post, listed under "cpu support" on the motherboard manufacturer's website. For ram, try checking the label for voltage requirements. You can change that in the bios on most boards. For power supplies, sometimes they simply don't work with certain boards. Try a spare ps if you have one.