I've had my 1st MBP for a few months now, have used it for a lot of home video, and would like to transfer this to an external hard drive, after which I might delete it from my MBP hard drive to free up more space. Does this sound like a reasonable way to keep open space on my MBP? Do I need to ever "defrag" this MBP like we've had to in the past for our old PC's? I'm still learning, but LOVE my MBP!!!! Thanks...