System refuses to power on. Mobo dead?

[Rock&Roll]

So I've decided to recommission my old C2D system for a database/web server project I'm working on.

(E6750, P5K wifi mobo, 4GB of DDR2)

It's been sitting in a closet for about 2 months with no power connected.

I dig it out and stuff a working power supply in it.

I power it up. It runs fine for a couple of hours.

I turn it off and come back a few days later ready to install Server 2008 on it. No action. When i hit the power button, the fans all spin for a couple revolutions and stop.

Tried clearing CMOS. Same result

Removed RAM and disconnected all HDD's and fans from the PSU. Same result, PSU would not stay powered up.

Removed the power supply in question an manually jumper ed the green start wire to ground. The PSU runs fine.

Tried bypassing the power switch on the case. No go.

Tried another power supply from my working main-rig, my 750W, to ensure it wasn't a supply issue. Same result.

Could it be that my motherboard is dead? Or is this a result of the mobo battery dieing after not being connected to power for a few months? The battery is putting out 3V, which is what it is rated for:/

I can't say I've ever encountered this kind of problem before.

EDIT. Never mind. It was a simple oversight. Can't believe it took me this long to figure it out

Mods, please feel free to delete this useless thread.