Are you trying to reinstall windows 7 AND put XP on it? If you want to install windows 7 ultimate, you will need the install DVD. For windows XP you also need the install disc. All you need to do is put the disc in your CD/DVD drive, and upon bootup press the setup key (F1, F2, F6, F10 or Esc for HP laptops, and go to Boot Order and move your disc drive to the top of the list. Save your changes and restart your computer. It should now boot from the windows install dvd.