My macbook pro is making a strange clicking noise, possibly the hard drive, I don't think it's the disc drive. It's quite quiet but consistent, it clicks about 14 times then stops for 4 seconds, then does it again. I noticed it about 10 minutes in to turning on my macbook, whilst I was playing the SIMS. The game completely slowed down, so I shut it down, and now almost all aspects of performance have slowed down and the clicking persists. Any advice or ideas as to what it could be? Many thanks, Sarah.