I have a late 2007 MacBook running OS X 10.5.8 that I upgraded with a Hitachi 200GB 7200RPM drive not long after I purchased it. It's been working great until about a week ago when I noticed a very quiet and frequent clicking/whirring sound coming from the drive as I was using it. My first reaction was that it might be the "click of death," but I wasn't getting any errors or having issues booting the machine, and the clicking was very periodic and not sudden like a drive crash. I verified the disk using Disk Utility and it checks out. I then opened up Activity Monitor and started watching the Disk Activity and sure enough I see a big red spike in I/O Data Written every time I hear the clicking sound, which is about every 20 seconds or so. Is my drive actually dying a slow, clicking death, or is there a rogue process writing to the disk and causing the sound? Is there a way to find out what it is?