[iBook] Noisy iBook

[Samantha Cornell]

We have two G4 iBooks (1.2 GHz, 768 MB, 20 Gig, 12", 10.4.2), both  
purchased about 6 months ago.  Within the past week or so, both have  
started making an annoying noise.  It appears to come from the top  
left-hand side, by the escape key.  It sounds like either the hard  
drive is spinning (noisily) or the fan is running (noisily).  Both  
machines seem to be hot, but likely no hotter than usual.

Has anyone experienced this?  Any idea what it is?  It's not horrible  
loud, but loud enough to be noticeable in a meeting.  Apart from the  
annoyance factor, I'm also concerned about the possibility that it is  
a hard-drive noise.

Thanks in advance for any suggestions.

Samantha