1. First understand that defragging your computer hard drive could take a while, sometimes even a few hours. So this is something you may want to start to run over night.
2. Choose Start in the lower left, then choose Control Panel, then choose System Security
3. Click Defragment Your Hard Drive and the defragmenter box will open.
4. In this open box you will see two buttons near the bottom. One is labeled Analyze Disk and the other is labeled Defragment Disk. Before you waste time, you can check to see if your disk even needs to be defragmented by clicking the Analyze Disk button.
This step will show you how fragmented your disk is. You only need to defragment it when it shows 10% or more fragmentation. Any less will not show you an improvement in speed.
5. Once the analysis is done, (if needed) click the Defragment Disk button. You will see the progress of the defrag under the Progress heading. When it is done, it will show that your drive no longer requires defragmenting.