You can't play DivX ;-) (aka MPEG4) on the Saturn. VCDs are MPEG1. You could try writing a Saturn player, but I seriously doubt you will achieve anything usable.
Considering Divx runs like ass on the DC, I doubt you'll get anything good out of the saturn. Only system that I see playing Divx's well will be the xbox
forget it.

divx are barely running on a dreamcast, and need a pretty decent PC to work too. saturn isn't all that easy to program for and simply not powerful enough.
Well, I suppose you could make somthing close to the VCD card, which would be able to run Divx. But then again, you would have to know the internal workings of the saturn so well it wouldn't even be worth it.
<table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr bgcolor="#333333"><td><font color="#FFFFFF">Quote (<font color="#FFFFFF">only chosen one</font> @ April 25 2002, 5:26 PM)</font></td></tr><tr bgcolor="#666666"><td><font color="#EEEEEE" size=2>Is there an easy way to play DivX movies on the saturn <font color=yellow>without</font> using a vcd card or <font color=yellow>programming anything hard??</font></font></td></tr></table>

The Saturn is already difficult to program; I don't see how it can get any easier.