Sometimes it happens that you forgot your password, but don't worry there are sometips which are useful to reset the password.
First,you can try this method.Start system and press F8 key when Windows is starting up. Then select Safe Mode with Command Prompt and enter. Choose Administrator,the default password may be blank if you don’t set the default administrator password before.Then you will enter into doc Command as following.
Type “ net user net user xxx 12345 /add “ (xxx is the locked account name and 123456 is the new password set on this account).Then you will see the Command Completed Successfully.
Then you can try ophcrack or Windows Password key .