It sounds like you have just copied the AVI file to the DVD. That won't work. It needs to be 'Authored', a complex process that transforms the AVI into the sorts of files DVD players understand.
DVD players are rather stupid (though the newer models are getting smarter) and don't have anywhere near the same computing power a PC does.. if they did they'd cost the same. So to make the DVD players cheap enough, the DVD standards people put a lot of smarts into how the DVD itself is put together.
A good authoring program can do a fair job of this. I personally prefer NeroVision Express 3 for simple DVD designs. DVD-Lab has a lot more flexibility, along with complexity. I seldom need it.
I recommend you get a good authoring program and learn to use it.
Fav quote - "Experience is whatcha don't get 'till ya don't need it no more."
System - Athlon 1.4GHz, Win98, Hauppauge PVR250 receiver and compressor.
Software -Magix Movie Edit Pro 10, Nero 6 + NeroVision Express, Moho 4.61, PSP 8.1, Bryce, Quicktime 6.52 pro, Goldwave 5, DVD-Lab.
Cameras - Panasonic GS9, Canon ES8400V, Canon EOS D20 and Canon A70