Blue_Gene

Try booting with the bare essentials again. Take out all of the parts outside the case and only re-seat the following computer parts:

Motherboard, cpu, one stick of ram, and then the videocard. If the computer still does not post, then for sure problem could be either one of these parts.

Try switching ram slots and see if that helps out. Also try clearing the cmos, refer to your motherboard manual for the cmos jumper location and instructions. Also you can try removing the bios battery for about 10min and put it back. Good luck!!