OT: tibook keeps making clunk sound

[Terry Richards]

my powerbook g4 keeps making a clunking sound. this happens in macosx 
and ydl. it doesn't stop until after all processes are stopped and the 
machine turns off. it usually starts after i access the internet with 
browser or mail. <but then i am usually on the net when using the 
machine > dsl>.  i replaced the hd once already and it stopped for a 
while. i have searched high and low on internet and have yet to find any 
solution. anybelly here know what to do about it or what could be the 
cause of it?

:-)^2