First try to show new features of vista in your slides and also how can u improve your system using vista, and thn some slides on vista security and you can also take some help from the web site which @satyams has mentioned. It would be good if you try to think by your self , because its easy to take ideas from others but really hard to develope your ideas so practice it from now. It would take only a full day i.e 24hours for some great ideas and you have got a full vacation , just give some hours to your home work daily.