I recently divided my HD into 2 partitions , c: with 82gb and D: with 61gb, using Windows Vista computer management. On C: I only have windows vista, MS Office and few small softwares. When I click on C: properties it shows that 37gb is being used, however, when I select all the files on C: (including hidden files) and click on properties it shows that the size on disk is only 15 GB. It is a 22gb difference, why is this happening? Is this normal?