After a disk has been used for a while, numerous writes and rewrites and erasures can separate data into bits and pieces scattered throughout a disk. Defragmenting or Optimizing a disk is a technique that takes pieces of information that have been written to separate regions of the disk and consolidates them into contiguous data units.
To run the defragmentation routine, click the Start Button, select Run and type in the word "defrag" (without the quotes). Clicking the OK button will produce the following dialogue box:
Selecting OK will tell the computer to take a look at the disk and see whether it needs to have this operation done or not. After a short time, the computer will return a screen that resembles the following:
If you elect to defragment, be prepared to wait and wait and wait. The larger the drive, the longer the process. Defragmenting is recommended if you create and erase lots of data.