This is day 3 as an Apple customer and so far this forum has been a ton of help! I would like to use the Time Machine program but it looks like I have to use an external hard drive, so I was thinking of buying a Western Digital MyBook 320 GB external hard drive which on the box says Mac compatible. Will I still be able to use the hard drive for other things on my Mac (like storing directory of photos or installing programs to?) besides a Time Machine back up or does Time Machine "lock" the entire drive? Thanks for helping a new Apple user!