C00D10D1 I have audio no picture

Recently my files which are in avi format have stopped playing. They had all previously played in media player, and i had transferred half of them on to dvd. However now i am only getting sound but no picture. This had happened at first but i downloaded a codec and they worked but now they no longer work, i have downloaded gspot, and it says the codec is installed...... what shall i do? Also when i tryto tansfer them into the DVD burner it says it cannot add the file because it is not valid or may be corrupt or......

well i have now made it work
i downloaded a file from this site http://www.divx.com/divx/windows/download/index.php
and then installed it and i can play the files in media player...
butit still says the files are no valid or a corrupt when i try to add them to windows dvd maker... i dunno any ideas?