Lost disk space

Recently I noticed that the free space on my C: drive had reduced by over 1Gb even though I had not placed any large files on the disk.
When I right click and select Properties (for the drive) it displays 5.88Mb of space USED yet if I open the drive select ALL files and folders (Ctrl A) and then right click and select Properties it displays only 3.88Gb as 'size on disk'. So where is the other 2Gb of space? Is it in Hidden and System files? How do I list those files? My swap file is only 511Mb.

 

even though I had not placed any large files on the disk

Oddly enough, small files cause more problems of this sort than large ones. If you are using FAT32 for file storage, the problem will be worse than with NTFS.

File storage is done using clusters. Different size drives with FAT32 have different cluster sizes and the larger they are, the less efficient. NTFS uses 4Kb for all but the very smallest drives. You can see exactly what you are using with NTFS by opening a cmd window and typing in fsutil fsinfo ntfsinfo x: (where x is the drive/partition you want to check so fsutil fsinfo ntfsinfo c: will do your C: drive)

If any part of a cluster is used by a file, the entire cluster is considered used by the OS and the empty part will not be used. So in theory, if you copied 1000 files of 1Kb each to a NTFS formatted drive, they would occupy 4000Kb (space used) even though the files themselves only occupied 1000Kb (size on disk).

By comparison, FAT32 uses 16Kb clusters on a drive larger than 16Gb so in that case, your 1000 files would be using 16000Kb of drive space.

In the beginning I said that lots of small files caused more problems because, for instance, a 2Gb file would still only use part of a 4Kb cluster above the actual file size so that 10 files of 2Gb each would only use 20Gb plus a maximum of an additional 40Kb.

http://www.microsoft.com/resources/documentation/Windows/XP/all/reskit/en-us/prkc_fil_lxty.asp?