[Gigabyte P965-S3] Is my mobo dead?

[tglembo]

Rosewill Case
Antec 480W PS
Gigabyte P965-S3
Intel Core 2 Duo E6600
NVidia 7900 GS
2GB Corsair RAM
500GB Seagate SATA harddrive

I have a homebuild which was running beautifully until yesterday when I decided to turn it off (haven't done that in weeks). I then tried to turn it back on and and the power light came on, it began to boot, and then shut down. I sat there for about 4 seconds touching nothing, when it turned back on and then booted up for about 4 seconds before suddenly turning off again. This cycle just keeps repeating.
I don't think it is the power supply (Antec 480W) because I hooked that up to an old Dell and the old dell was stable. I took everything out except for the processor and it still wouldn't stay on. I put the RAM back in and it still didn't work. THEN, to make me more confused, I put in a different P965 board that I had and it turned on and then off, just like before, but on the 2nd cycle it powered up completely and went into my OS.
So, can anybody help me? Is it my processor, mobo, RAM, or perhaps a combinations thereof?
Thanks!

 

[pavel-]

make sure you have a speaker connected to the motherboard and try booting up the machine with NO ram in it and see if it gives you the correct "Missing RAM" beeps as per your motherboard manual.

 

[tglembo]

I'm at work right now so I can't double check, but when working on it I tried to turn it on without the RAM just to see if it would not turn off (be stable). I don't believe that it gave me any beeps for Missing RAM. I will double check as soon as I'm home.
Also, had a friend suggest that the power button itself might be messed up although this suggestion seems quite weird to me...

 

[ComputersMakeMeIll]

Take out your C Mos for a few minutes and then replace. This will make sure its not something gone wrong with the Bios. Then go with checking those wonderfull beeps. Its really hard to count them and decide if it was a short or long, the power button is a tad weird but when you eliminate all the possibilities then whatever is left, no matter how improbbable must be the solution. To check your power button swap it for your re-set button.

 

[tglembo]

So I swapped the power button with the reset button and the problem persisted. Also, I reset the CMOS (took out the battery and shorted the jumper) and that did not fix it. Is it possible that the interface between the CPU and MOBO burned out so that both are now screwed? Awful if that is what happened. I tried hooking up a completely new MOBO and with the new MOBO it will go about half way through the post and then stop. Still no luck.