How did you come by a Dell product and not know the password? You can't change or remove it except by maybe contacting Dell support, prove to them that you're the registered owner, then explain to them how you lost the password (they will ask so be prepared to provide a good excuse). Otherwise you will need to know the password. Security was not invented to be easily circumvented. Doing so by yourself requires artful maneuvering (in addition to all the help you can gather from knowledgeable people).