I just recently purchased a used TiBook. The first thing I noticed about the computer was a faint click from the hard drive every 30 seconds like clock work. It is particularily noticable when it is dead silent in the room before the fan kicks on. I've heard failing hard drives and this is a different sound. I believe the people describing the parking hard drive heads are accurate. I've even seen a review of a new 17" Powerbook where the user describes the hard drive doing this (
See "Hard Drive "Clicking" Noise" under "Quirks" in this review). I'd like to visit an apple store to see if the Powerbooks there have this "clicking" as well.
Needless to say, once you notice the sound, it can drive you half nuts! It is not a random hard drive noise, but happens on my laptop every 30 seconds when the computer is idle or when I'm just surfing the web.
I downloaded the NoHDclickObjC.app from the link provided previously here in this post (Thank you Mick Angel, you truely are an angel!)... and activated it... no more clicking!
The NoHDclickObjC.app is now a permanent fixture in my dock (you have to activate it every time you start up). I wish I knew who made this application and the reason why it works, because I would gladly donate to the individual(s) who have saved my sanity!!!
TiBook G4 1GHz 15" Mac OS X (10.4.3) 1 GB Ram, SuperDrive