Are you logged in to the computer with an administrator account? You said that you have XP Pro, which should have the tabs.

An alternative to try, you can hit start, run, and in the box type control userpasswords2 . Choose the account that you want to use, and uncheck the box that says " Users must enter a user name and password ". I don't reccomend this, however, as it will automatically put you into a set account every bootup, and if you plan to surf the web or check E-mail, you should do so with a non admin account. Good luck!