This video demonstrates to viewers how to easily defrag the hard drive in your computer. To do a disk defrag on your computer: Click on the Start button. Go to All Programs. Click on Accessories. Select System Tools. Choose Disk Defragmenter. Select the drive you want to defrag (if you have more than one hard drive), and then simply click defrag. Wait for the defrag to finish, which could take some time depending on how large your hard drive is and the degree of fragmentation as well.