I want to sell or give away one of my dell desk top comptuers.  I was always told the only way to ensure none of your personal information gets into someones hands is to format the harddrive and reinstall windows.  Is this correct?  How do you do it?  I tried the old MS-DOS command but there was something running on the computer and it wouldn't let me reformat.  Any ideas on how to proceed?  Running Windows XP.  Thanks for the help!