ECS N2U400-A motherboard not posting

[RMSistight]

For some reason, the motherboard would power. All the fans would be running and the computer would not post. I've tested the following and they have worked on other systems:

CPU - Athlon XP 1800+
RAM - two sticks of PC2100 (one PNY and the other Kingston)
Video card - Radeon 9000 Pro 128 AGP 4X

I have to test one more item out and that would be the power supply. If the power supply doesn't change the situation, then I KNOW it's the motherboard. Any suggestions?

 

[bolomite]

check the 4 pin ATX 12V connector, maybe the connection is faulty

 

[RMSistight]

12V rail works fine. I used the ATX tester and the 12V line lights up while the +5V doesn't. Since there are two ground lines, I assume that's the 5V ones.