I have an iMac G5 and an ibook Intel core 2 duo that I think I should probably back up. I've never done that. Don't have a lot of stuff on these, but some short movies and pics, etc. Should I copy the OS, too. Don't remember if I got start up disc with the G5 a few yrs. ago, but may have them somewhere. Also, as I'm new to Macs, are there ways to clean up the computer as I have duplicates of a lot of pics.