Computer overheating

[Perndog]

My power supply started making funny noises about eight months ago. I shook the computer a little bit, and it stopped. It made more noises a little bit later. I shook it a little harder, and it stopped again. But eventually shaking didn't help so I decided to back up my files and live with it.

Today, my computer did an emergency overheat shutdown. After it cooled pretty well, I started it back up and checked it out and noticed there was almost no airflow coming out of the power supply. While I was at it, I also noticed that the CPU fan is going in fits, too. If I tap the power supply, it works better for a little bit. I'm guessing my still-working intake fan and exhaust unit are the only things saving my CPU and motherboard from a meltdown, though since it's happened a couple of times already, I expect the BIOS will do a good job of stopping things before actual hardware damage occurs.

I'm posting because I'd like to know if I can repair the power supply fan or if I'll have to just spring for a new power supply entirely. I'll probably drop $200 on a new motherboard and CPU no matter what, since the computer's over three years old (speaking of which, tell me which brand of motherboard I should buy--I'll probably go for an Athlon 64 mb/CPU bundle), but I don't want to spend the money on a new power supply and perhaps new case if I can just fix the fan myself or have one of my computer geek friends do it for ten bucks.

Thanks.