I was wondering if I have a 7200rpm hard drive in my MBP, will I have to buy an 7200rpm external drive. I would think that you wouldnt need the speed of 7200rpm if it is just a backup and not the main drive, but if they would not be compatible that would be important to know. Also, do only certain external drives work with Macs or does any USB or Firewire external work? Thanks so much and Merry Christmas!