When files are stored on disk they are stored in blocks. A set of blocks can be contiguous or fragmented. Contiguous means adjacent. A contiguous file is composed of a sequence of blocks that is stored in an unbroken chain. A fragmented file has gaps in the block sequence, and the gaps are usually occupied by blocks that belong to other files. If a file is fragmented, or non-contiguous, the hard disk has to skip expanses of blocks as it tries to read a file from start to end, which means that fragmented files cause slower performance.
A fragmented hard disk is a disk that has a lot of fragmented files. A defragmented hard disk means faster read/write access, which, in turn, means better overall disk performance.
Regularly defragment your hard disk, every week if necessary, and certainly at least once a month. Also defrag your disk after deleting a large number of files, cleaning out your browser cache, uninstalling applications, or after using the Windows Disk Cleanup Utility.
The Windows XP Disk Defragmenter is a crippled version of a commercial product called "DiskKeeper" and has a number of limitations:
The User Interface is not intuitive.
The defragmentation process is rudimentary at best.
Large gaps are left between individual files, i.e. the disk is not compacted.
It can only defragment one volume at a time.
It cannot be run on a schedule
While the built-in XP defragmenter is ok for average users, power users who need more from a defragmenter might consider looking at UltraDefrag, which is an Open Source defragmenter for Windows that supports both x32 and x64 versions of XP and Vista. UltraDefrag offers:
Very fast defragmentation, the work is done via a kernel mode driver that has an optimal defragging algorithm.
Very small engine written in pure C.
The full download is under 200k in size.
Nice graphical interface, which is both compact and functional.
Safe, because file moving is accomplished with Microsoft's own Defrag API.
Simple to use.
Can generate html reports of fragmentation status.
Can include/exclude files based on simple filters.
Free: Distributed with full source code under the GNU General Public License.
Has a Compact option to remove gaps between files
If you decide to use defragmentation as a performance-enhancing tool then also download and install Microsoft's PageDefrag tool. Most defragmenters cannot defragment pagefiles and registry hives because those files are open while the defragmenter is running. If you want to optimise your pagefile and other system files, especially if you have only a single hard disk, then this tool is highly recommended.
Using the 'select remote users' button, you can select user accounts that have access to the computer remotely. All members of the administrators group (that is, the built in 'administrator' account and any users who were added during the install process) are allowed remote access automatically.
