When you save a file to your hard disk, it tries to keep all clusters (parts of a file) together. This allows your computer to retrieve a file quickly. Eventually files are deleted from your hard disk. This leaves empty spaces between the remaining files. If a large file is then saved, the hard disk must break the file apart and store clusters in empty spaces all over the disk. This process is called disk fragmentation. It then takes longer to access files from the hard disk. See also DEFRAGMENT.
