No additional software is needed for DVDs though some will make your life a little easier. Did you update the registry key to add the "dvd library" tile? If not, start there.
Add the update the below registry setting and a "dvd library" tile will replace the "play dvd" tile on your Media Center Start Menu.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Media Center\Settings\DvdSettings]
"ShowGallery"="Gallery"
From there most users will start collecting cover art and creating DVD xml files (see http://www.dvdxml.com/ as a good reference). You can do this manually or use any number of the free tools available.
If you have a Media Center Extender you might also want to take a look at http://www.htpcug.org/Default.aspx?tabid=168.
If you need more information give a look through the forums as there are tons of posts about this. If you need help I can try and point you in the right direction. Ashleigh has also put togethor a good list of items @ http://www.nakedcleaner.com/2008/06/30/media-center-stuff/.
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