Codec problems

Archived from groups: microsoft.public.windowsxp.video (More info?)

When I try to edit my avi. files in microsort movie maker or any other video editing program it tells me, depending on which program and file, that I don't have the DIV3/DVD-DivX/XVID codec to decompress and edit the file yet I can still watch the files with windows media playerand unless I'm mistaken that means I already have the codecs, right? Please help because I plan to burn these files to cd to watch in my dvd player and their to big so I thought I would split them and burn to two disks instead. If you know how to fix this problem or solve my dilema with a program that could split them without so much hassle please reply. Thanks