One of the drives (an IBM of some description) in my main desktop machine started intermittantly clicking three years ago (when it was a couple of years old) and is still struggling on. It spins down sometimes when it is feeling particularly unhappy, waits 10 seconds and spins back up. I've been expecting it to fail for at least 2 years now...

Don't worry, my all data is stored on my server ;-)
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Remind me to change my signature to something more interesting someday