I think mine just failed last night. It's been running (literally) 24/7 for over four years since I bought it. I was never even aware that there had been an issue, until now. So, I'm basically left with tearing my HD out so I can off-load the data onto another computer.
Sucks eggs. But luckily the computer has been little more than an email machine for a few years.
But if I were you, I would do a complete HD backup on yours, now, to save that extra step if your machine WERE to fail soon. I can't even boot mine off a system DVD to do anything - which I've posted about here - with no helpful responses yet.