You can also go in safe mode an create a new user name as administrator then delete his old one, this will save you from reinstalling

Log on using the administrator account, the default password is none (blank) (in case you don't see the administrator account, at the log on screen hit ctrl+alt+del twice and at the new log on screen type administrator as user, leave blank the password and hit OK). After you have logged on you do what you wish.

In case of a problem or clarification, don't hesitate to post.

Thanks and regards
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Stelios