Perform a clean Windows reinstall.  But this is least advised method as has potentials of vital data loss
Employ a third party Windows Password Recovery Software.

To modify a Windows password, Use another user with administrator rights.  Maybe the most obvious thing to do, but not everyone knows that a director user can change the passwords for all other users also.  If you still know the password for a different director user, this is the way to go.

If last idea failed to work, you can opt for another one.  The subsequent idea is all about resetting of passwords.  As agreed by Microsoft’s Window support information base, you can set a new password easily -
- If you have typed the wrong password, you may receive a message that says your user name or password is incorrect.  When this message appears click OK.
- Click Reset password, and then implement the instructions.

Windows XP and later versions also provide an alternative way for Windows Login Password recovery with the “hard reset”.  When you make a password reset disk in the past, you can use this disk to reset passwords.

I personally recommend using a third party password resetting software. This works well for non tech persons. posse.