[doggyfizzel]

Pretty much the hard drive on my Macbook keeps randomly spinning up. It never normally does this except on start up. Anyone know what this might be a symptom of? Imminent HD failure?

Here a youtube video with the same noise, except mine will do it during use or just idling on the desktop. I have the same model.
http://www.youtube.com/watch?v=ZUYydBgxDPI

[iisjman07]

I'm a computer technician and hard drives don't make that sound, however, slot loading dvd drives make exactly that sound. The vast majority of slot loaders will make a sound when initially powered on to test whether there is media inside, it's nothing to worry about.

If you're worried about your data then use Time Machine or similar to backup to another medium.

[theronkinator]

Yeah that's definitely the disk drive not the hard drive. I used to be an IT Tech as well (and my Wii makes the same noise ).