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How to Defrag a Hard Drive

A little preventative maintenance goes a long way when it comes to your Windows-based PCs. All Windows operating systems come with tools that you can use to help keep your computer running in top shape. One such tool is the Disk Defragmenter (defragment), which works to optimize fragmented files on the hard disk drive.

Fragmentation describes the condition of your hard disk drive when files are divided into pieces and scattered around the disk. Fragmentation occurs naturally when you use a disk frequently, just by doing basic tasks like creating, deleting and modifying files.

At some point, the operating system needs to store parts of a file in noncontiguous clusters. This is entirely invisible to you, but it can slow down the speed at which data is accessed because the disk drive must search through different parts of the disk to put together a single file. In a nutshell, the Disk Defragmenter will optimize a disk by unfragmenting the stored files.

How Disk Defragmenter Works

When you run the Disk Defragmenter it will perform several tasks. The application will locate fragments of files stored in different locations on the disk and then copy them into a single continuous file at a point on the disk that has enough free space. It then compares the two files and updates the Master File Table (MFT). After writing to the MFT, the Disk Defragmenter will then delete the old fragmented file and the MFT is again updated with the new free space information.

How to Access the Disk Defragmenter

In Windows XP or Windows Vista you can access the Disk Defragmenter tool through the following steps:

  • Click Start, select All Programs, select Accessories, select System Tools, click Disk Defragmenter. (or)
  • Open your Windows Explorer and view all drives. Right click on the drive you want to defragment and select Properties. In the Tools tab choose Disk Defragmenter.

In the Disk Defragmenter tool box, you'll need to select the hard drives you want to defragment. In Windows XP you can Analyze the drive first. A user interface will show you the progress as you run Disk Defragmenter. In Windows Vista there is no graphical view of the progress as the application works.

Defrag in Vista
Defrag in XP
Screenshots showing how to access Disk Defragmenter in Windows Vista (above) and Windows XP.
(Click images for larger screens)

It May Take a While

The Disk Defragmenter tool can take anywhere from minutes to hours to run, depending on the size of your hard drive and also how fragmented the drive is. One way to run the Disk Defragmenter and not lose any computing time is to leave the system and run the Disk Defragmenter during a time when the system can be left on but is not be in use (e.g., 3 or 4 a.m.). You can simply use the steps above to launch Disk Defragmenter when your computing tasks are done for the day or you can have the Windows Task Scheduler automatically run the Disk Defragmenter on a certain day and time each week or month. In Windows XP or Windows Vista you can access the Task Scheduler tool through the following steps: Click Start, select All Programs, select Accessories, select System Tools, click Task Scheduler.

Tips for Getting the Best Results

  • Ensure you have no applications running when you start the Disk Defragmenter. If you system is accessing applications the Defragmenter will not stay running. Be sure to turn off your screensaver also.
  • Delete your Temporary Internet Files and other files you do not use. You can also uninstall unused programs. In the Properties tab of your hard drive you can access "Disk Cleanup," which will help you get rid of unused and unnecessary files.
  • Run the Disk Defragmenter at regular intervals. However you can also run the tool if you add a lot of files to the disk at one time or find you are running low on disk space.

Based in Nova Scotia, Vangie Beal is has been writing about technology for more than a decade. She is a frequent contributor to EcommerceGuide and managing editor at Webopedia. You can tweet her online @AuroraGG.

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