HELP!!! 30 -40 min presentation!!!

[shoreshotfl]

Hello all!! I have a job interview with an IT firm that is requiring me to do a 30-40min presentation. I am supposed to be selling myself to the company. In the past 3 interviews they have inquired alot about traits. I guess what I am asking is where do I begin with this? How do I go about selling myself for a sales role? is a powerpoint slide show required? the instructions from the HR person said I could use one or flip charts or nothing at all, and they have no expectations when it comes to visuals. My main issue is how do I begin this presentation?? Do I spell my life story in 30min or do i touch on achievements in my life?? PLEASE HELP!!! what would you do???