From the amount of information on Google,I take it you may not have looked any? I can not recommend an exact program. But there sure is alot of information and programs available to do this. I would suggest you read up and download something and try it out.
Actually I did look but the only thing I typed is "decode divx" and then I got confused so I gave up and went to techspot. Sorry, I dont have time to check links right now I gtg.