I think we need to define what the process of decrementing does
The Windows operating system is a reasonably efficient OS when it comes to dealing with files, when you write data to the hard drive the OS fits parts of the data into areas on the hard drive that are empty of data so if you save a 500mb file to a drive the OS may split the file into many parts installing each part into an area that may have been occupied by data from another file that has been deleted, When files are updated, the computer tends to save these updates on the largest continuous space on the hard disk, which is often on a different sector than the other parts of the file. When files are thus fragmented, the computer must search the hard disk each time the file is opened to find all of the file's parts, which slows down response time.
Disk Defragmenter consolidates fragmented files and folders on your computer's hard disk, so that each occupies a single, contiguous space on the volume. As a result, your system can gain access to your files and folders and save new ones more efficiently. By consolidating your files and folders, Disk Defragmenter also consolidates the volume's free space, making it less likely that new files will be fragmented.
@ ketamininja
Instead of increasing wear and tear on the hard drive it must actually decrease ware and tear because the heads have less work to do to find and access files.
@ Simon
If you have the disk defragmenter running in the back ground then you don?t need to run the program separately, the program will keep you hard drive defragmenter automatically by running only when needed, i.e. when saving new data to the hard drive
Brian