who

So I was happily working away on my desktop pc, when all of a sudden it dies. No shutdown, no reboot, just off.

Then it wouldn't boot. It would get past the device detection, and then turn off again.

Now I can't even get that far. I can get some power into it if I hold the on button.

First I suspected the worst, a HD crash. Now I'm thinking the motherboard could be fried or something, but I hope it's a power unit that needs replacing.

Has this happened to anyone in here before? What do you think it is?

BTW there's no funky burnt smell coming out of anywhere, and I'd feel safer if there was one coming out of the power supply.

I've checked connections, etc., everything is fine, and, as I said I was working at the time, there was no excessive overheating, I don't think.