Start the computer in 'Safe Mode' by pressing key F8 as soon as you switch on. You will then get a screen asking you to make a selection as to how you want to boot. Select 'Safe Mode' using your cursor keys (the 4 arrows pointing to all points of the compass) then press 'Enter' and when the computer has booted to 'Safe Mode' run Disk Defrag. This way you will have no programmes running in the background and Disk Defrag will run straight through without interruptions. The Windows Help Page will probably load as you are booting into 'Safe Mode' just close it down so you can see the desktop.