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If you do not know your Windows password, and your computer resides on a domain, contact your network administrator to have your password reset. If your computer is not on a domain, you may be required to reinstall your version of Windows. " Your computer will then inform you that your Windows password has been changed to reflect the new password.
Power on your Windows 7 or Windows Vista computer. Select your user account and enter your password, if applicable on your machine. Press the "Control," "Alt," and "Delete" keys simultaneously. Select the option labeled "Change a password. Type your old password and a new password into the fields provided. Press "Enter" on your keyboard.