Boot up problem

I've had this setup for a year.Asus p5w premium and Pentium D805 with ddr2 800 memory.I upgraded the motherboard,cpu and memory.so I pulled out the motherboard in tact with cpu and ram installed and stored it for a while.I decided to use the old motherboard,cpu and ram for a home theater setup so I bought a new case and ati 2600pro.I tried to power it up before I installed it in the new case,Just motherboard, cpu,memory and video card.It wouldn't power up.I disconnected the 4 pin aux power cable and it powered up with cpu fan running,but no display.Plugged the 4 pin aux power cable back in and it wouldn't power up,just the green light on the motherboard and I don't get any post beeps.powered up with no ram installed and still no post beeps.Is this a bad motherboard.Oh and I tried another PSU and checked both PSU's with a tester.Help

try it out side the case to rule out shorts but first clear cmos by pulling battery and sitting ctr jumper to 2/3 for atr lest 10 min.s
Rich

It was outside the case.

did you clear cmos
Rich

Cleared cmos.

Would it power up with the fans running and cpu fan running with no post beeps or video if its a bad CPU?What confuses me is that it won't power up if I connect the 4 pin aux power cable.

sounds like a short what kind of hsf is there a back plate on it
Rich
might take the cpu out and see if you have a bent pin