Fans run when computer is plugged in, but PC won't boot??

This is strange.  When you plug in this computer the fans start running and the hard drive spins.  (The power button has not been pressed.)  When you push the power button the rear case fan stops running.  The computer never boots, but it does seem like the power supply is getting juice to all the devices.

Here's what I've done so far . . . the power supply has been replaced since that was the low hanging fruit.  All of the cards, HD, and other connections have been pulled so those devices aren't interfering.  Same result.  At this point it looks like it's either the mobo or the cpu.  I'm waiting for a replacement mobo tester in the mail, so in the meantime any probability it's one vs the other?  This computer is less then 1 year old so neither of these parts should be an issue, but stranger things have happened.  

Thoughts?
cunninwAsked:
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Grizzly072000Connect With a Mentor Commented:
From experience, I'll bet for the board....
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Grizzly072000Commented:
You seem to have gone through all the steps.
Are you looking for bets: MoBo against CPU?
Less than 1 year? I wouldn't have bothered & just sent the whole thing for warranty replacement.
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cunninwAuthor Commented:
Sure, I'll take bets . . .

From a practical perspective II think I'm going to try a replacement CPU first since that's the easiest to put in and out.  
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Grizzly072000Commented:
Oops: I realised we have forgotten about the memory. Please run Memtest or equivalent (He he..., much easier than replacing a CPU)
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cunninwAuthor Commented:
I've switched memory in and out AND in and out of different slots.  I can't get anything on the screen or the computer to turn on for that matter so I can't run memtest (or I would have).

I'll let you know.
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Grizzly072000Commented:
Did you try resetting the CMOS (Jumper or remove battery for 30 min.)?
No POST beep(s)?
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