Custom Built Computer Won't Turn On

Hello all, I have a pretty seriously problem with my home built computer. I have had it for about 7 years now and every two years or so I just upgrade a part on it. About 5 months ago it just stopped working and the harddrive failed. The power would turn on about once every 50 times i pushed the power button. So to clarify things, my computer would not start up, but if I kept pushing the power button and messing around with he power supply, the computer would finally start up.

Recently I decided to try and fix this problem and I drew the conclusion that it was either the motherboard or the power supply causing the problem. I bought them both and low and behold STILL WOULD NOT TURN ON. Now this new motherboard had a power switch on the board itself, which when turned on would trigger the lights of the motherboard so I would know the board was getting power. Whenever I pressed the power button on the board I would get nothing, no lights, no fan starting up, nothing.

So this brings me to my question. If a computer wont even turn on and it doesn't seem that the motherboard is even receiving power... what could it be.

Here are my specs.
4G DDR2 RAM
2 80G SATA hard drives
CPU- AMD Athlon 64 x2 'ADA5200IAA6CS'
Motherboard- EVGA nForce 730a
Power Supply - BFG ATX 2.2
Graphics Card - Nvidia 8600 GTS

So I would really appreciate the comments. All I can think about is the CPU now being bad, but I don't understand why that could affect power capabilities. From research i have done, the Motherboard, CPU and Power supply are all compatable with each other.