It sounds like the hardrive maybe failing.
The hardrive makes an irregular noise as it reads/writes data, and when these begin to failure they make a clunk noise, often repetitive clunking.
However, if this noise is perfectly regulkar from the second you turn on the machine until you turn it off, and it seems to be working fine, then it would appear NOT to be the hardrive and can only leave the option of some sort of failing fan bearing maybe???
A strange description. Can you add more information?
Drew
DrewKrew, March 2011
