http://mediacoder.sourceforge.net/

It may seem crappy from the website, but it works great, and converts everything, and its free. I've used it for several lectures/presentations I've made for converting stuff from YouTube (FLV) to either AVI or MPEG4/MPEG2.

You can definitely convert AVI to MPEG4 (DVD), so no worries. Hope it helps. ;\)