Summarize this article in one sentence.
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.

Summary:
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.