Since this is an important thing that people should be doing i would like to know how you back up your mac. I use carbon copy cloner and i back up every week or so. I have two internal hard drives, one is 250GB which has my main OS on. My 2nd internal is a 500GB hard drive were i have my itunes folder (lots of movies), ripped movies and anything that needs lots of space. I just drag the the folders in the 2nd hard drive after i backed up my main one.