Kind of what MustISO said, but it is possible.
Take a look at
VideoHelp and do a search for DIKO. It's a freeware program that will convert AVI's, author, and burn to DVD all in one step. Fairly easy to use. However, be aware that the conversion process can take several hours depending on your CPU and length of video.
I don't think it's possible using just NERO6, but in my limited experience DIKO works great.