ok i'm not only going to tell you the answer to you question but i'm going to teach you how to search for information... ready?
the answer to your question is set the book type to "dvd-rom"
now if you need further info on how to do this there is a very good guide, just use the search button(top far right of page) and type in what you'd like to know, that way threads that have been made many, many times don't get re-created
not trying to be rude, just educate the noobs