How to Defragment Your Hard Disk

If your computer doesn't seem to launch programs or open files with the same pep as before, hard disk fragmentation might be part of the problem.

Fragmentation is a normal result of creating and deleting files, but if it becomes severe you'll notice your PC getting sluggish. The good news is that you can often speed it back up by defragmenting your hard disk. Let's look at how fragmentation occurs and what you can do about it.

What is Fragmentation?
To understand what fragmentation is, it helps to know what happens when files are deleted and created on your hard disk.

Deleting files on your computer creates gaps of free space on your disk. When you create a new document, image, or other file, your computer tries to write all of the file's data into the first available area of free space.

But sometimes that space isn't big enough to hold all the data. When that happens, your computer writes as much data as possible in that space. Then it finds free space elsewhere on the disk and stores the rest of the file's data there.

Over time, your computer stores more and more files in this way, scattering fragments of individual files across your disk. When your computer opens a fragmented file, it has to retrieve the data from several different areas of your disk, slowing down the process of opening files.

Defragmenting (or "defragging") rearranges the data on your hard disk so that each file's data is stored in one location. This allows your computer to find and load the data more quickly and efficiently.

Before You Start
There are a few things you should know about disk defragmentation before you jump in:
  • Although defragmenting is normally safe, there's a risk of losing data if a power outage or some other problem interrupts the process. So back up your important data to a removable medium, like a CD or Zip disk, before you begin.
  • Depending on how large your hard disk, defragmenting can take several hours, and you can't use your computer while it's happening. Start it before you leave for work or before you go to bed.
  • Your disk should be error-free (see computer maintenance tutorial for details about checking your hard disk for errors).
Defragmenting in Windows
Windows includes a utility called, appropriately enough, Disk Defragmenter. Before you run it, shut down all other running programs (including background programs like virus scanners and screensavers). Other running programs can interfere with Disk Defragmenter, causing error messages.

If you shut down all programs and still have problems running Disk Defragmenter, you might have to clean boot your system or restart it in Safe Mode first. Instructions for doing so in Windows 98/Me and Windows XP are available on Microsoft's Web site.

To start Disk Defragmenter:
  1. Click the Start button and select Programs (Windows 98/Me/2000) or All Programs (Windows XP).
  2. Choose Accessories, then System Tools, and finally Disk Defragmenter.
  3. Select your hard disk in the Disk Defragmenter window if it's not already selected.
At this point, if you're using Windows 2000 or XP, you can simply click the Defragment button. If you're using Windows 98 or Me, follow these additional steps:
  1. Click the Settings button.
  2. Make sure Rearrange program files so my programs start faster is checked.
  3. If you already checked your disk for errors, uncheck Check the drive for errors to save a little time.
  4. Click OK to close the dialog box, and then click OK again to begin.
Defragmenting in Mac OS
The Mac OS doesn't include its own disk defragmenter; Apple's position is that fragmentation doesn't affect a Mac's performance "significantly." But if you want to wring every last bit of performance out of your computer we recommend investing in a third-party utility. Popular choices include PlusOptimizer from Alsoft, Tech Tool Pro from Micromat, and Norton Utilities from Symantec.

Before you buy a utility, make sure it specifically supports the version of the Mac OS you're running. And make sure to read the documentation for the software you choose thoroughly before you use it.

If you can't or don't want to lay down the cash for a third-party program, you can go with Apple's suggestion: Back up the contents of your hard disk, initialize your disk, and then restore your data. Note: Initializing destroys all the data on the disk, so make sure you have a complete backup before you do this!

Set a Schedule
How often should you defragment your hard disk? There aren't any hard and fast rules, but we can offer some suggestions that work for a lot of computer users. If you often work with very large files (like audio, video, or graphics files), defragging once a month will help you maintain your computer's performance. If you usually work with small files, defragging once every two months should be enough.

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