What to do if the movie that you download can't be read by your car dvd player?  

hey i think there is a problem in your dvd such as it doesnt know how to play the codes. i advice you to convert the movie into a format which your dvd is supposed to read, there are many video converters in net so check out them

The movie will be in a format based on the MPEG4 standard, such as avi or divx. Some DVD players can play such formats, although there are still many that will not.
The movie will require decoding into either MPEG2 or vob files in order to allow the player to read them. You can recode through many burning programs, such a Nero Burning ROM etcetera, or you can download one of several freeware video decoders.

First of all you need to check your dvdplayer brand and search internet about its features and see which video format it supports.if it supports mp4 then convert the movie to mp4 using TOTAL VIDEO CONVERTER;-)

Check your car dvd player manual for the formats that it can play. Some dvd players cannot play avi format. So you need to convert the movie to a format that the player can read for example into an mpeg format. My Sony dvd player can play almost any format, mpeg, divx, avi. When you purchase a dvd player, you should check the dvd formats that the player can read.