There are numerous apps that you can use to convert divx files for pocket pc usage.
Windows Media Encoder is free from microsoft, and can basicaly convert any file playable by Windows Media Player (meaning, have the codecs for the file installed, like divx) to a wmv format. the
www.bigdsvideo.com website has some explenation on that as well.
WMV files can be played by the usualy build in Media Player on your ppc.
To convert to DIVX, VirtuaDub is basicaly the handiest program, and again, look on the website for it how to use it.