Won't power on

A friend sent me a known working X7DCA-L with dual Xeons and memory and I just hooked up it up in a case w/ power supply that I had lying around but it won't power on.

When I plug the power in the first green LED turns on. Then I push the power button and another green light comes on as long as I hold the power button but nothing happens.

The power supply is an Antec EA-500D. The 8 wire power is hooked up, and then the power supply has a 20 wire connector and an additional 4 wire, with the motherboard requiring a 24 wire. I am assuming that since the 20 wire fits the shaped connector right, and the 4 wire also fits all 4 shaped pins and is properly fitted to slip in right next to the 20 wire, that this is supposed to be there.

According to the Super Micro manual I need an ATX power supply 2.02 or above. The Antec website says this power supply is ATX 2.2 so I again assume I'm correct putting the 4 pin directly against the 20 pin to fill the 24 pin socket.

Mobo manual
http://www.supermicro.com/products [...] 7DCA-L.cfm
Antec product info
http://www.antec.com/pdf/flyers/Earthwatts_US.pdf

Am I missing something here?

You are correct. It requires 24 pin sockets. And the power supply is also ok. What I am thinking is that there must be some problem with power supply. I mean it is dead or something licks that. Just hook it with any other board and try.

Power supply setup for that MB is;
The X7DCA-L can only accommodate 24-pin ATX power supply. Although most power supplies generally meet the specifications required by the motherboard, some are inadequate. You should use one that will supply at least 400W of power. In addition, the 12V 8-pin is also required for adequate power supply to the CPU. Also your power supply must supply 1.5A for the Ethernet ports.
It is strongly recommended that you use a high quality power supply that meets ATX power supply Specification 2.02 or above. It must also be SSI compliant (info at http://www.ssiforum.org/). Additionally, in areas where noisy power transmission is present, you may choose to install a line filter to shield the computer from noise. It is recommended that you also install a power surge protector to help avoid problems caused by power surges.

So you need above 400watts, one 24 pin conn JPW2, and one 8 pin conn JPW1
http://www.supermicro.com/manuals/ [...] L-0985.pdf

Did you also make sure all the power connections were added as well, mine needs three different pwr connector, 24, 8 and 3pin.
I am using a C7P67 MB