do you have the debian cd?
if so pop it in your cd/dvd drive, reboot (and you'll see the installer appear).
If it doesn't show up, make sure you set the cd/dvd drive as first boot device (e.g. in your bios).
Oh one thing, if applicable, make a backups of important data you want to be able to restore.
Last edited by teebones; 01-15-2011 at 01:43 PM.