Introduction

File fragmentation occurs when a file, be it data or a program, is not saved to a contiguous place of a computer's hard drive.  If a word processing document is spread over three places it will take three times as long to load since the drive has to read it from all sections.  Since hard drives are already one of the slowest parts of the computer it makes sense to arrange files into single contiguous locations.

A common complaint about defragmenting a hard disk is how long it takes or errors that occur when doing so.  

Here are a few tips depending on your operating system:

Windows 95, 98, or ME

Taking into account the capacity of newer hard drives, it is a good idea to begin the process when the computer will not be needed for a period of time.  Remember that using the system will cause defrag to restart itself.

The process will be interrupted if you have programs running in the background such as a virus scanner or even screen savers.  Some files don't like getting moved around while active in memory, getting paged to virtual memory, and so forth.  Therefore, I recommend defragging while in safe mode.

The easiest way to start a 95 computer in safe mode is to hold down the F8 key before the splash screen appears.

To start a 98/ME computer in safe mode, either hold down the F8 or the Control key prior to the startup splash screen.

Windows NT/2000/XP

Generally speaking, 2000 and XP's interactive graphical defrag program does not care as much about other running programs and starting in safe mode is not necessary.

To relieve yourself of remembering and making a point to take the time to defrag regularly, automate it.  Windows XP has graphical and command line defrag utilities.  MS KB article 555098 referenced below has step by step instructions to automate defragging in Windows XP.

Windows Vista

Windows Vista's defrag utility is dumbed down.  No longer does the defrag window show the status or any visual indicators of fragmentation.  It also seems to be very slow.  I have been evaluating various free and retail products.  When I find something suitable I will post it in the Everyday Software FAQ.  In the meantime you may feel free to start a thread in my forums with recommendations or your own trials and tribulations.

http://www.auslogics.com/disk-defrag/index.php

Further reading and useful links

http://support.microsoft.com/default.aspx?scid=kb;en-us;186978 Microsoft's article about running defrag in Safe Mode

http://www.ultratech-llc.com/kb/?File=Defragger.TXT Andrew Baker's FAQ with third party utility recommendations

http://support.microsoft.com/default.aspx?scid=kb;en-us;555098 Microsoft's instructions to configure automatic defrag in XP

http://www.schmahl.net/pcsetup.php addresses pagefile fragmentation in the Advanced Optimization section

http://www.adopenstatic.com/cs/blogs/ken/archive/2006/12/26/919.aspx A blog by Ken Schaefer about Vista annoyances pertaining defrag

http://www.kessels.com/JkDefrag/ free defrag for Windows 2000/2003/XP/Vista/Windows X64