As I sit here and type this on my new MacBook Pro, the HDD is emitting a faint but noticeable "tick" sound every 10 seconds or so. It only occurs when there's not a lot of HDD activity. For example: I started a big render going in Final Cut Pro before I slept last night, and it wasn't ticking; when I woke up this morning the render had finished and the ticking had returned. I'm therefore assuming it only occurs when the HDD is relatively idle. I didn't notice it until the day after I bought it, probably because I was installing a lot of software updates initially. Has anyone else noticed this noise? My old PowerBook G4 occasionally made a sound or too but nowhere near as regular or high-pitched. I'm finding it hard to sleep because the noise is slowly driving me insane! At first you don't think it's a big deal, but it quickly becomes like Chinese water torture! My first thought was a 7200 rpm HDD might fix the problem, being a different drive and all. I'd love to hear from new MacBook Pro owners of both 5400 and 7200 rpm drives so I can decide whether I should take the machine back and swap it.