Hi. I have a 1TB Seagate external hard drive. Today, I erased the entire hard drive using disk utility (with one pass of zeros). However, once it finished erasing disk utility still showed 663.6 MB as "used" with 58 files. Yet when I open up the hard drive using Finder I can't see any files. I also tried formatting the external hard drive as FAT...which dropped the number of invisible files to 0, but still about 684kb was used for "something." Finally, I formatted it back to Mac OS Extended (Journaled)...the file system I want...and the 663.6 MB of invisible data magically reappeared. So what is this data and how can I get rid of it. Thank you.