I want to burn a dvd from movies on the internet

you will have to use a program called dvd shrink if its a real dvd as this takes it to a size that fits onto a dvd r it also removes copyright protection

You cannot do this without re-authoring the VOB files in a video editor. The reason is that one of the VOB files is an index file that tells the DVD logic chip what to say on the screen. When you reauthor, you get to change that file. In a nutshell, use a video editor to create two single files of the two movies, then import each of them into the video software - say Power Producer or something like that, Create a startup page in the program and have each movie as a chapter, or individual chapter each movie in 10 minute increments inside a folder that gets selected by the menu. This is a lot to absorb but this is how.

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if you want to burn a movie in a stand alone dvd player you need to convert the avi to dvd .vob format first.

If your dvd can play divx along with vob (dvd) format then just burn the avi using the data dvd function you maybe able to put 3 or 4 movies on a 4 gig dvd. This will not work on a stand alone dvd player.

how long have you been using the burner? does it burn data and audio completely? try cleaning the lens with lens cleaner and check the CD/DVD you are using to burn your movies. also try using another burning program

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Check the file format.