Computer Problems

So I just wrote this really long lost on the new CF ads, and then my computer crashed. I am very heart broken. I have to jet to class, but I will try to reconstruct it tonight.

In the meantime. I need computer help.

Since this summer my computer has taken to sporadically turn off and then make this omnious sound: "eee ooo eee ooo eee ooo eee".

Yeah. Not good.

I know it's not software. I've had the computer for three years and I've already replaced the power supply once. It's a build-computer from a ma and pop shop but should have some good components.

It's a AMD Athelon XP 2500+ 1.84GHz 512RAM

Now I'm sure it's an overheating problem because I'm bad and leave my computer on ALL THE TIME.

I do use a dust can on it religiously and vaccuum it out twice annually.

After my computer does this, I turn off the power bar and turn it back on. Reboot the computer and it's up and running fine.

This problem has happened in London and Peterborough and I've changed the power bar and the sound still happens.

If anyone has any advice or specific diagnosis: ie. it's the motherboard, it would be much appreciated.

P.S.: Also I've already backed everything up on CD, so if it decides that it doesn't want to turn back on again, I'm good to go.