Have you tried a different power supply?

You need the 4 pin ATX 12V connector to power the cpu. Withoui it, there will be no boot, because the CPU does not get any power.

Now, as for your problem, there are 3 possible sources, bad CPU, bad PSU or bad motherboard. If the PSU is known good, it is likely the motherboard, it is virtually never the CPU in my experience.

My suspicion is either dead capacitors or dead power phases. That your board only has this behavior when the 12V plug is connected pretty much narrows it down already to the CPU and/or its VRMs.

I can try a different CPU and see what happens

The PSU is brand new and works when connected to a different board

Smack2k wrote:

I can try a different CPU and see what happens

Isn't that one of the boards that for some strange reason (ask nVidia why) only supports the first generation Core 2 quads and not the second (45nm) generation?

I don't think they have any issues with later 45nm dual core CPUs or "pin (pad) modified" 45nm Xeon 54xx quads though...

According to the sites I've checked for processor compatibility, it supports the Q9550.

Also wondering if the fan / heatsink is on too tight as it's really on there. That a possibility?

Well, according to product site, board should be compatible with that C2Q 9550, but you have to update BIOS for support of that CPU!

Do you know, which version of BIOS and which CPU revision are you using?

I need to check but first gotta get an older core2quad proc (Q6700) I have in it and see what comes up, if anything. That one requires an older BIOS so hopefully works. If not will drop a Core2 Duo in it and check...

Q6700 seems to be supported with initial version of BIOS. If motherboard and PSU is are alright, it should work, even if BIOS was untouched.

Different PSU, Q6700 CPU Installed...Same issue, starts and immediately stops on boot....

All I have setup in the board on a cardboard box, Mouse, Keyboard, Video Card, Known Good RAM (1 Stick of 2 GB), and the PSU......

EDIT - Its acting the same way it does with no CPU / Heatsink attached to the CPU as it does when the CPU / Heatsink is attached.....could it not be recognizing the Heatsink / Fan?

When plugging 4/8-pin EPS CPU power makes board not do anything, it's either PSU or MB.
If PSU is fine, something shorts 4-pin or gets too hot, which makes board shut down within seconds.
Check if thermal pads and paste on VRM and chipsets are worth anything at this point.
Overheating chipset/VRM can make this problem occur.

If everything else fails, you can try forcing board to not shut down by manually connecting green and black cables on 24-pin (while it's plugged in board).
HOWEVER there is HIGH risk of VRM type of failure shortly after board stays powered after notmal shutdown point, so DO NOT install ANYTHING on that board when doing this test.

I noticed the heatsink over the Chipset and VRM was really loose. Upon releasing the feet, I found that one of the Chips is all busted up.....no clue how it got that way, but it explains things...

Board is a loss....onto another one!!

Thanks for all the help!!