What is the best program for converting avi/divx files and burning them onto a usable dvd?
You have several choices:
If your DVD player supports DivX then you can just burn them to dvd as data files without converting.
I use ConvertXtoDVD. It is not free but works very well.
I use DVD Flick which works great and it is FREE, and you may find the options for the volume and sound track very handy