I have a late 2009 MBP that was running out of hard drive space. A month ago I bought a 750GB Hitachi Travelstar hard drive to replace the original one. It worked great for about a week. Then I started hearing a periodic clicking noise. I called Hitachi and they said that the drive was going bad, so they sent me another one. I installed the new one and then put the failing drive in an enclosure and tried to use disk utility to erase it before I sent it back. That's when it failed. It no longer works. The 2nd replacement was fine for a few days, but then I started hearing the clicking sound again, so I put my original drive back in and put the replacement in a hard drive enclosure. I booted from the drive that had been clicking, but it isn't doing that anymore. What gives? The times when I would hear the noise were when the MBP was good and hot (had been running for a while) but was sitting idle such as when I'm reading something and not loading any files/apps. Do you think it's just the hard drive? Any advice would be appreciated.