Defragmenting a hard drive, or more accurately, a file system, involves rearranging the bits of data on disk so that all of the pieces of a file are laid out in sequence. As data is written to a disk, many small chunks of a file can be spread over a large portion of the hard disk. Over time, this lack of organization can result in a very significant performance impact, much as your day would be shot if you have not defragmented in a while. Be sure to turn off the screen saver before doing this, or it may interrupt the process.
To access the Defragmentation utility in Windows 2000 and XP:
1. Click the Start Menu
2. Click All Programs
3. Click Accessories
4. Click System Tools
5. Click Disk Defragmenter.