Hi, I have a 500mhz Tibook and lately my fan noise has gotten a lot worse.

It sounds like it's not able to maintain speed and makes an oscillating sound. It's spinning, but sounds like it's getting resistance. It's hard to describe, but it kind of sounds like a bleating sheep. Can I clean it with compressed air?

I also noticed that I'm missing the center screw on the bottom of my case. Could that be contributing to the noise? Do you sell them?

I read somewhere that the processor heatsink screw(s?) can come loose and contribute to the fan running more often. How can I check?

Thanks!