This video teaches you how to change your computer's account password using the DOS command prompt. The first step is to get to the command prompt, you can do this simply by clicking run in the start menu and typing "cmd." You next type "net user" which will show you all of the user accounts on the computer. Choose the one you would like to change the password for and type "net user (account name)." It will then ask you for a new password, you may type anything you like here keeping in mind that for security reasons you will not be able to see what you're typing. Then type it a second time.
Upon the next start up the computer will need this new password to access that user's account.