Download WinAvi converter, install it.
Open it.
Click the "DVD" circle in the bottom right corner.
A thing will pop up that will let you browse to where the AVI file you want to convert is.
Click the file. (If there's a movie that's broken up into 2 AVI, pick them both but make sure part 1 is above part 2 in the box below "Files that will be converted".
Then choose an output directory (where the new converted file will end up)... Mine is my external harddrive but you can use your desktop.
Then make sure the output format says DVD.
Click Ok and leave your computer so it can convert the movie (Usually takes 30mins-1 hour depending on the size of the movie).
When it's done you now have a .VOB file that can be burned easily with Nero and will work in a DVD player.
(The file should be in a folder called DVD_01 or something wherever you chose to save it, you can rename it though.)
NOW TO BURN...
Open Nero.
Click Nero Express.
Click Video/Pictures, then click DVD-Video files.
Click add. Select ALL the files in the VIDEO_TS folder only, the audio_ts folder is useless.
Click next, then burn, then VOILA. In 3-10 mins depending on the files the movie will burn.
Enjoy.
