gateway won't boot no video cpu fan don't spin

I have a gateway e series flat tower. P4 1.6ghz I upgraded to 2.0ghz. It will not boot I have tried swapping psu, cpu, cmos battery. The orange power button light comes on and green led mobo light is lit and the cpu fan pins for 1 second and stops. It has agp nvidia graphics card no onboard video but has square 4 pin connector beside cpu. I disconnected it and I heard the hard drive spin up and cdrom like it was booting but no video and the cpu fan didn't spin. I have tried another fan in both cpu and case fan power pins. It was working fine than i turn it on and this. I have tried memory too but didn't work.

 

psu replacemnt should fix it!

 

I tried that. It didn't work. Could bad caps make it do that?