However, when a disk has been in use for some time and a variety of files have been saved to it and some have been deleted, the available storage space is probably spread out throughout the disk and the disk is said to be fragmented. When this happens, more directory information has to be stored and it takes longer to load files as they have to be gathered up from their various locations on the disk. For this reason, it is often worthwhile copying files from an old disk on to a new one and then reformatting the old one. This is also true of hard drives, and certain utility programs can defragment the hard drives. One of the most common problems with any personal computer is that people occasionally delete files accidentally.
Hard Disks drive failure can occasionally happen.
If your Hard Disk fails there may be no way to recover any of the data on the drive. If you did not have those files copied to a back-up diskette all your work may be forever lost. Once infected, the only solution may be to erase all memory in the computer and start with a clean sweep. If someone steals your computer, your files get stolen too. Backing up is easy if you set your folder structure properly.