Computer not even reaching POST, no beeps or anything

[Haircut]

OK, my PC has suddenly decided not to work today.

I'd been away over Christmas and got back yesterday. I turned my PC on and it worked fine.
I have been having a few issues while shutting down recently though, occasionally it will turn itself back on up to a few hours after shutting down.

This is what I thought had happened this morning. I set it to hibernate last night, come this morning the power light was on, fans were on but nothing from anything else, USB devices were showing no signs of life.
So, at this point I did a hard reboot.
It powers up again, all the fans go, hard drives spin up but nothing else happens. There are no beeps, it just sits there with the monitor in powersave mode.

At first I thought it might be a power supply issue, but I've swapped that out and it made no difference.

I suspect it's a motherboard issue, it's a couple of years old now.
Motherboard is a MSI K8N Neo4 Platinum (Socket 939)

Any suggestions as to what else I can try to diagnose the problem before biting the bullet and buying a replacement would be welcome.

EDIT:
I should point out that it did boot up fully once this morning, then just reset itself after about 10 minutes.
Now whenever I try it I just get nothing.

 

[melbourne720]

perhaps strip it back to just PSU, CPU, mobo, RAM, see if you get a beep?

 

[Cyber Hamster]

I would try and rule out the PSU and memory first as both of those can cause odd things to happen. ie try using only 1 stick of ram at a time if you have 2, if you can get hold of another PSU that you know works try that as well.
If not then I would suspect the mobo.

 

[Haircut]

Thanks for the suggestions.

I've already tried another PSU with it and still the same issues.

I've just been playing about with it again though and it booted up and got as far as the Windows logon screen before restarting.
It then got as far as the POST screen before restarting again and did this about 10 times until it went again.

I've also tried taking all my RAM out and starting it up, basically to purposefully do something which should cause it to beep on start and I got nothing at all.

Hmm, looks like it's going to be a choice of either finding a socket 939 motherboard from somewhere or upgrading to a Core 2 Quad setup