yes i know you need an external Hard Drive got that check.. my deal is i have a Mac Pro thats 1.5 TB in total HD Space I have Used 550 GB. Ok i started Time Machine and selected my 500 gig External HD, I wanna backup everything on my Mac Pro and I have selected everything but about 250 gigs of music so that makes 350 of backup. When Time Machine goes to backup it says it needs a total of like 880 gigs available on a HD for time machine to work? ... any help?