The Defragment program is a useful utility but sometimes the message that Windows sends can be deceptive. Often when you access the Defragment program you get the following message:
Drive C:\ is 0% fragmented
You don't need to defragment this drive now
If you want to defragment anyway, click Start
Defragment anyways. Sometimes you may have just removed several megabytes of files from your hard drive, but Windows doesn't recognize the large number of empty clusters scattered throughout your hard drive.