Disconnect your hard drive and optical drive until you can get it to post. Also unplug anything you don't absolutely need for the PC to post, like USB printers, external drives etc. I might even disconnect the front panel audio cable, USB header cables, and leave only the case power button connected. In rare cases I've seen a PC not post if the power LED or hard drive activity LED was connected back wards. Start with the bare minimum, power supply, motherboard, CPU with heat sink, one stick of RAM. Once you can get it to post into the BIOS, then start plugging things back in one at a time.