Powerbook Squeeling Noise

It could be the fan inside the PB, its in that general area, and with the AC adapter plugged in it would cause the computer to run faster thus hotter, so it require the fan to be on more, so I guess either your fan is scraping something inside. Or your fan unit is defective.

Actually, a high pitched squeak is normal in all powerbooks. Check out this thread to make sure it is not the noise you are describing. You can also try a search, as the issue of powerbooks and weird noises has been brought many times befoe.

Some noise is 'normal'. That said, its never fun to have a noise. I think the fan is the cause of this noise, as it was in the case of my Wife's powerbook.

We had Applecare and they replaced the fan and no more LOUD noise. There is still a power supply like noise when plugged in, as the other user reported.

The problem is if the fan is slow or defective, your powerbook could overheat and become damaged.

While I agree that a damage fan is an issue that should be taken seriously, I really don't think that is the case here. The way Scorched X describes the sound as a "squeeling noise" and that the noise is at it's loudest when the processor is running at the highest speed, leads me to beleive what is being heard is the typical powerbook noise. People often report that setting the processor speed to highest increases the frequency of the squeak, and that setting it to automatic instead helps minimize the noise.