? 
Guess, the only option is to re-install
http://windowshelp.microsoft.com/Windows/en-us/help/66b61e8e-341d-453b-9edd-234301dfd7e51033.mspx
What to do if you forget your Windows password
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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.
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To use your password reset disk to reset your password | ||||||
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To use an administrator account to reset your password | ||||||||||||||||||
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