As someone who works a lot of computers, this is actually quite worrying. I've had my MacBook Pro for several months (Penryn), and it has a clicking hard disk. If i start it up from cold, its okay for a while... very very quiet even on read/write, until say 10 minutes.... then the clicking starts. Sounds very much like the hard disk heads parking themselves constantly every 15 or 20 seconds. CLICK................. CLICK................... CLICK. There is no clicking on big read/write operations. CLicks also very in loudness... they get louder... or if the machine is on my lap and i'm in a noisy room I can FEEL the clicks. Sometimes the clicks go away if i sleep the machine and wake it back up again. Everything seems to check out... the SMART status and ran a verify in Disk Utility. I am assuming this disk is unlikely to fail as i would imagine it would have done so by now. Its just very very annoying. If i replace the disk myself do i automatically void the warranty even if i dont damage anything?