I'm quite new to Mac. I have mac book 13.3" and I recently found that my disc space is low. When I check the HD size on desktop (cmd I) it says capacity 111.47 GB, available 18.72 GB, used 92.75 GB. Now When I open the HD and go item by item I'm missing 17.31 GB as I have Libary 7.13 GB, Applications 3.18 GB, system 4.14 GB, User guides and information 4 KB, Users 60.99 GB. This is altogether 75.44 GB so I should really have available about 36 GB. Can somebody help me please?