If you've forgotten your Windows password and you're on a domain, you should contact your system administrator to reset your password. If you're not on a domain, you can reset your password by using a password reset disk or by using an administrator account.
If you forget the administrator password and don't have a password reset disk or another administrator account, you won't be able to reset the password. If there are no other user accounts on the computer, you won't be able to log on to Windows and will need to re-install Windows.
You will not be able to follow these steps if you have locked your computer.
If you have typed the wrong password, you'll receive a message that says your user name or password is incorrect. When this message appears, click OK.
Click Reset password, and then follow the instructions.
If you use an administrator account to reset the password, you will permanently lose access to any e‑mail messages or encrypted files that are on that account.
These steps cannot be completed on Windows Vista Starter, Windows Vista Home Basic, and Windows Vista Home Premium.
Log on to the administrator account that you will use to reset the forgotten password.
Open Local Users and Groups by clicking the Start button , typing lusrmgr.msc into the Search box, and then pressing ENTER.
If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
Double-click Local Users and Groups, and then click Users.
Right-click the account that you need to reset the password for, and then click Set Password.
Type and confirm the new password.