Copying data files (documents, spreadsheets, databases, graphics, photos, music, etc.) from the computer's internal hard disk to a secondary medium, such as a removable hard disk, external hard disk, CD-RW, DVD-RW or tape cartridge, should be done routinely, because the hard disk can self-destruct (see head crash). There may be more paranoia about this subject than the number of incidents, but they do happen, so it is extremely wise to make backups. Backing up is also called "archiving." Using the Copy Function For small backups, you can drag and drop files and folders from the hard disk to the backup medium whenever you wish. However, you have to be aware of the file and folder sizes you are copying and the size limitation of the target storage device. If all the files will not fit, you can use a compression program to reduce the files before copying them. See archive program. Using a Backup Program There are several advantages to software designed specifically for backup. First, backups can be scheduled on regular cycles or every time you save a file. Differential backups can be made, which copy only files that have changed rather than the entire folder, which saves time. Compression can be applied automatically to save space. Backup software can automatically span multiple media if there is not enough room to back up everything on one disk or tape cartridge. There are also backup utilities that make a full copy of the entire hard disk, which enables you to restore full operation of both software and data in the event of a hard disk crash. Re-installing applications is extremely time consuming. Even if the original installation CD-ROMs are available, you may have applied several patches and updates to the software and made numerous personal configuration changes. See cloning software. Nevertheless Your data are more important than your software, so as long as your data are backed up, you will not lose the Great American Novel that took you 10 years to write. See backup types and data recovery.