I have a 80 gig hard drive (74.1 gigs recongized) and I use it to store my linux iso's(cough), mp3's bought from the internet (cough), and a back up for another smaller hard drive. It says I have used 68.4 gigs of it, but when i added up all the folders (including hidden ones, which were none) on the drive it only comes out to about 50 gigs. Where has the ~18 gigs gone to?