Ok heres the deal. Every time I try to export a movie in iMovie or burn a disk in iDVD an error message pops up and says that my startup disk is full. So I bought an external hard drive and backed up my mac using Time Machine. Now I want to delete everything off my mac's internal Hard Drive and use my external hard drive so I can empty my disk. Does this make sense? If so will you please tell me how to do so.