Can somebody help me with this, the last two AVI files I downloaded have no video only audio. 
posted in Audio Codecs
The best thing to do would be to feed them into a diagnostic utility like the ones mentioned here
http://www.moviecodec.com/topics/61931p1.html
The audio tag number will indicate which audio codec you need. If it’s tag 8192 (2000 in hex; the name box will say AC3), then install the ac3 filter http://sourceforge.net/projects/ac3filter/.