Getting to know the Sansa Media Converter

Hello all I am brand new here with this being my first post.  I had a question about the media converter.  I downloaded it and it worked fabulously for puttting some pictures on my Fuze but last night I decided to try to put a movie on there.  I went ahead and paid the $1.99 to get the digital copy of The Dark Knight that came with my DVD.  I downloaded it onto my harddrive.  I then figured I would add it to the media converter and it would put it on the player but no dice.  It said that I didn’t have the correct codec which had me scratching my head because I thought that’s what the converter would do for me is put the Video in the correct format that the player needed.  Can someone explain how I might get the movie on the player?  Do I need additional software?  I would also like to copy some other bought DVD’s to my harddrive and convert them to be able to play on the computer or the Fuze.  Is there any free software to do this?  Preferebly a one stop shop type of thing that will save it then I can convert it if I want?  Any help or recommendations would be very appreciated.  I’ve had my Fuze for a couple days and love it so far and plan to buy my wife one in the next day or so.  Thanks.

any video converter there’s a free version to convert to avi format