PC not starting up at all

[gwaves]

Okay, I'm completely burned out because of this.

So, I built a system out of both old and new parts. I fixed everything up and I press the power button. The Power Led lights up but nothing else happens. If I press and hold the power button the led goed off. No fans are spinning, there's no screen etc.

First I thought it could've been the PSU, but after trying 3 others the same problems was there. Then I thought it was RAM, but nope. Then I switched mobo, no go.

What exactly could the problem here be?

 

[Proximon]

Start here:
http://www.tomshardware.com/forum/261145-31-build-post-checklist

 

[gwaves]

Start here:
http://www.tomshardware.com/forum/261145-31-build-post-checklist

Everything that's stated there is correct. I've done many custom build PCs, that's why this one is so frustrating for me. I'm 99% sure something is not working properly but I can't find out what. If fans don't spin it's usually the PSU, but the power led goes on so it must be something else.

 

[Proximon]

Ok, so post the full parts list please.

 

[gwaves]

ASrock p4v88 mobo
Intel Pentium 4 3 GHz CPU
1GB Kingston valueram
Radeon X1600 Pro
Old PSU, 300 watt, 15A on 12V rail

WD 1TB, Caviar
LG GH22
Elite 333 case

I think that's all. Pretty much all the parts are old except for the last 3.

 

[Proximon]

If you have really ruled out bad motherboards, in that you are certain the other board you tried was working and FULLY compatible with the CPU, then I guess you are down to the processor.

Just don't assume that because a motherboard has the right socket, that it supports any CPU that fits in there.