Your hard drive is like a book with thousands of pages. Every time your computer writes a file to the hard drive, it starts writing at the first "page." As files of different sizes are deleted and written, when your computer writes a file, it may use a few pages here, then skip forward to the next empty page, then skip forward to the next empty page after that. This process of breaking files into pieces of files is called disk fragmentation. When your disk is heavily fragmented, it's more prone to errors and will actually cause your system to run a little slower. Defragmenters move around these pieces of files until they all line up. Running a defragmenter every month or so is good system maintenance, especially if your hard drive is almost full.

If you have Windows 95:

1. Go to the Start button.
2. Go to the Programs folder.
3. Go to the Accessories folder.
4. Go to the System Tools folder.
5. Click on Disk Defragmenter. Choose the hard drive you want to defragment, then follow the onscreen instructions.

If you have Windows 3.1x:

1. Close Windows and go to the DOS prompt.
2. Type DEFRAG and hit <Enter>. (If you see the response "Bad command or file name," you may be running an earlier version of DOS without built-in Defragmenter. You'll need a third-party program, such as Norton Utilities, to defragment your drive.)
3. In Defrag, choose the drive you want to defragment ("optimize"). Click OK.
4. After Defrag checks your system, click the Optimize button.