I would reseat the power supply leads to the motherboard (remove and reinstall all the leads to the board, optical and hardrives. Do this with the power supply unplugged. When you plug it in, notice if any motherboard lights come on; most newer boards have an indicator light when the board is receiving power. Also be sure your ps toggle switch is in the - position (on the back). Get rid of the paper clip. Finally, be sure your case leads (power switch, power led, reset, etc) are positioned correctly on the correct pin cluster. It's a common mistake.