Dead motherboard?

Hey guys.
I've got a PC to fix which I fixed last week.

Last week I just had virus removal etc, I ran it for 6 hours straight to make sure everything was good.
I also built this PC, it's actually my old dual core AMD machine.

So she took it home and it just wouldn't fire.
I now have it back and have swapped out 3 different PSU's, 1 of which I know 100% works fine.
All I'm getting it a quick whirl of the CPU fan and then nothing, just the green mobo light.

I've removed all but 24 pin and 4 pin motherboard connectors, removed RAM, GPU so it's just the mobo and CPU.
Same result.

This suggests a dead motherboard to me, but I would like a second opinion.

The only thing I can think would have caused this is it sat in my car all day, in temps of 2C - -2C, then she took it home and plugged it in cold (I forgot to tell her not to do that)

Any ideas?

 

You ran through most of what I would do.

Is the PROM removable, and have you reset CMOS?

 

I haven't reset the cmos, might give that a go.
But what is PROM?

 

The prom is the chip which stores the BIOS ROM.

If it is removable, you can "flash" it, or in layman's terms reprogram it externally.

Try removing the CR2032 battery for at least five minutes, and then attempt a boot.

Excesively low temperatures could scramble ROM programming.

Or, that just may be an urban legend...