In the effort to use Time Machine, I want to partition my external drive. I have 500 gig external, and would like to have one partition of 480 and one around 20. This way, Time Machine will only back up onto the smaller partition, not endlessly backing up until all 500 gigs are used. The reason I need to partition without erasing is my 170 gig iTunes library. Its too large to transfer to my internal HD, and I have no other drive to store it on. Anybody have any ideas?