I purchased a new 15inch mbp and swapped the hard drive to a new WD 640gb model. The macbook pro is a quiet machine which has meant that the most apparent noise is hard drive idle noise. I noticed there is a substantial amount of headspace above and below the hard drive. I stuck Small squares of 3mm thick rubberised foam on the four corners of the hard drive on the bottom and top side to provide a firmer fit for the hard drive. (not too firm mind you, by design the the hard drive has a small amount of room to move on all sides, as it helps with knocks) The vibration in the drive is reduced and the computer is noticeably quieter. Has anyone done anything like this or has some other tips or suggestions. I love a quiet computer.