I've recently noticed that the hard disk on my C2D MB (which I bought in November) is making a regular clicking noise (each click is about 30s - 1min apart) when using programs as well as when it is idle. I don't remember hearing it as often as this in the past (it would make the noise for a little while and then disappear)...is it anything to worry about or is it just normal activity? I was told it could just be OS X defragmenting files in the background or is it something more sinister? I have run the Disk Utility and the S.M.A.R.T. status is "verified". The hard disk is a FUJITSU MHV2080BHPL.