ibook G4 buzzing

[iWishmycomputerworked]

My ibook G4 has recently taken to buzzing much more noisily than it used to. Then earlier today, the buzz built to a whine and the ibook froze. After a forced shutdown and a half hour to cool off (although it was on a level wood desk and did not seem hot) I hit the power button only to hear a blood-curdling screech, and startup took much longer than it should.
Anybody know what this means?
(it's not the speakers, it seems to come from left of the trackpad. unfortunately I'm pretty sure that's the hard drive or maybe a fan?)

 

[Egidio]

If you have the original installation disk, pop it in and re-start your Mac holding the C key. Then from the original disk, run Disk Utility and repair permissions as well as Verify Disk. See if the reports shows any problems.