Would it be possible to back up all my music, pictures, etc. on my external, wipe my hard drive, and then put it all back on, without an issue? I ask because I feel like there's hidden things taking up space that I want to get rid of. I think when I set up my mac about two years ago I messed something up when generating a use profile, and copied my iTunes music TWICE, and now that is still hidden somewhere and I can't find it, upwards of like 20 gigs just eating space. Thanks.