They do have 4x3 menus in the DZ. Download them if you need it. Preview those created like before 2008 and you'll see black bars on the left and right of the background picture on some of them. There will be no black bars when you use it on a 4x3 dvd. Black bars will be on the menu background picture on a 16x9 dvd.
Some of those menus will cause problems if used in PD13 but not with older versions of PD. Here is one example of a 4x3 menu:
http://directorzone.cyberlink.com/detail/76498 . To me, an excellent menu from an excellent designer. It will crash PD13. I modified it to work with PD13 on one of my projects.