(First world problems)

For the past 3 days, our MySkyHDi box has been unusually noisy - I believe the noise is coming from the HDD. What puzzles me is that it seems to be louder when in stand-by mode and not recording than when on and/or recording.

When I first heard the noise 3 days ago, my first thought was that a light aircraft was flying over. Anyway, noise aside, it's working fine. I have tried to power down the box and a soft reset but no change. Has not been moved (it gets a wipe down with a rag every week when dusting)

It's also fairly full - about 70%-90% most of the time. I've had this since launch, Juny/August 2008?

Any ideas on the cause? HDD Failure/Internals wear and tear due to vibrations?