Hey, my 27" iMac has recently started doing this constant chattering noise with the hard disk. it doesnt sound like intense disk activity but its like its doing some background loading or something thing is... activity monitor reports zero reads in and zero writes out... so according to the computer the hard disk is doing nothing, or should be doing nothing. But clearly from the sounds its making, its doing something. What gives? I am about to praise the ground apple care and time machine walk on?