I'm all new to Mac, and need help! What's the best way (easiest) to back up all my data? iTunes, what & how is the best way to back up? Have a MacBook Pro, and am new to Mac but like it. How do I free up memory so it will stop saying startup disk is full? What is it that's causing startup disk to be full? I have a lot to learn since I've been a long time PC user. Thanks!