Over time and with regular use, files and folders on a computer's hard drive break down or become fragmented. This can cause the system to run slowly and to experience processing problems. Defragmenting the computer generally improves retrieval time and overall performance.

For example, a computer program must access various files on the hard drive every time it is run. If those files are spread out on opposite sides of the hard drive instead of gathered and organized neatly, as they are supposed to be, the computer will have to work extra hard and take extra time to access the information it needs. In some cases, severe defragmenting may even cause a program to stop running entirely.

Defragmenting, also referred to as "defragging," reorganizes the hard drive by putting pieces of related data back together so that files are organized in a contiguous fashion. As a result, the computer system can access files more efficiently. By efficiently organizing files and folders, defragmenting will leave the computer's free space in one big chunk. This will allow new files to be saved in an orderly fashion, thereby reducing the need for future defragmentation.

As the overall size of disk drives keeps increasing, defragmenting a computer regularly may even help to increase its life-span. A system needs to work quite hard in order to collect fragmented information across larger and larger disks. Considering the amount of work this takes, it seems likely that defragmenting can help a hard drive last significantly longer.

Though some computer experts argue that today's operating systems are efficient enough to eliminate the need for defragmenting altogether, it is generally recommended that computer users defrag their systems on a regular basis. Average users will probably find that bimonthly defragmenting produces sufficient results. Users who notice a frequent loss of efficiency and speed may choose to defrag more often.

All computer systems come with some type of defragmenter tool, commonly found under the "System Tools" option in Windows-based PC environments. Such tools typically come with an analysis feature that will actually tell users if their computers need defragging or not. You can also defragment disks from a "C prompt" command line using the "defrag" command.