Have a pc here thats just stopped turning on.

I've taken everything out of it so the only thing left connected to the mobo is psu and cpu. Now when i turn the power supply on at the switch at the back it turns on straight away as in cpu fan starts spinning and posts (pc speaker beeps to say theres no ram/gfx etc) without me even pressing the on button.

I also don't seem to be able to turn it off using the power button either - only the switch on the back of the power supply.

I've tested this with another known working power supply and it is doing exactly the same thing. I've even disconnected the wires that go to the power switch in case that was shorting.

Do I start to look at a new motherboard or is there anything else i can try?

Try a different PSU otherwise it's time for a new board (which is most likely). How old is board?

Sounds like its pwned.

Try without the RAM and with a PC speaker connected. Thats a fairly quick and easy way to tell if a board is alive or not.

If no beeps it generally means the mobo is toast.

Yeah as I said i've taken everything out including ram and used another powersupply.

With its original psu it powers up for a split second - enough for the cpu fan to spin once or twice then nothing - no power or anything.

With another known working power supply it turns on and beeps because there is no ram.

Which makes me think its the power supply but what concerns me is that at no point have i pressed the switch on the front of the case. It turns on the second you turn the power on at the back of the power supply.

The board is 2 years old
MSI K8N Neo4 Platinum AMD Socket 939 Motherboard

Some mobos have a bios option to auto turn on when power is present so they kick back on after a blackout/UPS ran out of juice.

ok yeah you could be right actually - i think i read something in the manual about that. Considering i've just reset the cmos that'd be it.

Ok looks like its just the psu then. Thanks