how do I log in as administrator

on what had been this windows xp system I had been logging in as
administrator. Now when I boot Vista I dont even login and my user
name is my name, not administrator.

assuming and hoping everying like my email which appears trashed on
this PC is that way because I am logged in as a different user than I
had been .... how do I login as adminstrator?

when I go to start ... switch user I only see my user account. Where
is the administrator account?

thanks,