When windows saves files to your hard drive, it doesn't look for a space big enough to hold the entire file together, instead it stores pieces of the file in whatever spaces that it finds on the disk. When you add to an existing file the entire file is not necessarily moved to a new location, the existing space can be reused to store part of the file with the rest of the file being stored elsewhere. When a file is stored in pieces in different spots on the hard drive we refer to it as a fragmented file. A fragmented file is slower to read that one stored all together because the drive has to search for the location of each piece separately.
As time goes on the content of our hard drive becomes more and more fragmented and the system performance will be reduced. To resolve this problem Microsoft has included a disk defragmentation program as one of the windows utilities.
The defrag program can be accessed from an option on the Tool tab of the drive Properties dialog box of any hard drive on your system or alternatively can be accessed by selecting Start then Programs then System Tools and then selecting Disk Defragmenter.
Once the defrag program starts, the first thing you need to do is to select the drive that you want to defragment. If you just have one hard drive in your system and do not have it partitioned then you need to select C:. You can also go into the Settings to set a number of options to be used by the defrag process. The options you can set are: Rearrange program files so my programs start faster (which will put exe and dll files for the same application next to one another), Check the drive for errors (which will run scandisk before starting to defragment), This time only which doesn't save your settings for future defrags and Every time I defragment my hard drive which saves the settings.
When you select OK on the defrag dialog box the defragmentation process will start and will rearrange all of the data on your hard drive so as to reduce the number of fragmented files as much as possible. While the defrag program is running you don't want any other programs accessing the hard drive as this will interrupt the defrag process resulting in the defrag starting over again. You probably want to turn off any screensaver while you defrag as well as any other programs that you normally have running in the background that might access the hard disk. You also don't want to be trying to do any work on the computer while the defrag is being performed. Since defragmenting your hard drive can take a significant amount of time you may also consider the option of leaving your computer on overnight and starting the defrag just before you go to bed. Even the largest hard drive should finish defragmenting within a few hours.
Once your hard drive is defragmented you should notice an improvement in the performance of your system when accessing the hard drive.
This article written by Stephen Chapman, Felgall Pty Ltd.