What happened to your memory modules? Check everything for loose connections..

I have tried each of the mem modules individually. I have checked and re-checked connections. A few minutes ago I put the old motherboard back in. Same thing...except the case power button works, unlike with new motherboard. I have cleared CMOS. Even if mem was dead, shouldn't I still get a POST attempt?

Like my computer, the processor fan spins when the power supply switch turns on but later it stops spinning. It is normal.

Try to boot it in bare minimum setup. Troubleshoot them outside the case, place your motherboard with processor, memory, video card, and power supply in a non-conductive material outside the computer case. Locate the power switch terminal on the motherboard then temporarily short it by a small screwdriver tip then release it. Check if it will boot.

Should the power supply be pulled from the case as well? I just tried it with MB outside case...PSU in. Still no go. I also tried with a known working mem stick.

Not really needed to pull it out but it is better to place the power supply near the motherboard in order to have a room for the connection. Detach all wires terminals from the motherboard and put a mark on them so you can easily return them again later. Remember, place the motherboard on the non-conductive materials in order to prevent it from short. Connect the wires from the power supply to the 20 pin and 4 pin sockets of the motherboard. Be sure the monitor is attached to the vga socket.

1. Did you turn it on through the motherboard terminal? It's wires from the power switch button on the front panel of your pc case to the motherboard. So that you can determine if the power switch is sticky or broken.

2. Did you clean the contact of the memory stick before inserting it to the dimm socket? Use a pencil eraser to clean the contact and reseating it to the socket several times. Use one stick at this time then restart your pc.

3. What video card do you use? Is it integrated to the motherboard or pci video card? If pci card, clean its contact with a pencil eraser several times then insert it to the slot. Then restart your pc.

Check if it will boot.

Please specify your new motherboard make and model..

fren....I've started it via the case button and by shorting the pins.....No POST
I've cleaned and swapped memory
I've used an AGP vid card and tried the integrated, still no POST.
The motherboard is an ASROCK P4i65G, my non-new one is an ASROCK P4VM800.
I've built several pc's in the past and have never come across a no POST situation.

I think either the motherboard or processor is the problem. Do you use ddr400 in your new mb? Processor type, please?

P.S.:

Why don't you try swap their processor and motherboard? Since they are both almost compatible.

Yes I have ddr 400. The processor is a p4 3.0(prescott) brand new direct from intel. I sent them my old one as I thought that that was the problem.