DivX and XviD are not supported as standard on the N800, however they should play ok with mplayer.

Supported video formats as standard: 3GP, AVI, H.263, MPEG-1, MPEG-4, RV (Real Video)

Use Media Converter to convert video first if you intend to use internal player. Here's a link:
https://garage.maemo.org/frs/?group_id=26

If you need to use DivX movies, you need to install mplayer. That should be able to show divx movies out of the box, although performance for higher rez movies is still in tuning phase as serge doesn't yet have a N800.

I ran the media converter on a few divx files that I had, in order to make the prerequisit files for the n800 (I used the "mplayer best solution", or something like that, setting) and when I played the files they looked great, but moved in fits and start, both in the stock media player, and in mplayer. The files themselves never quite stopped playing, but it was like somone was hitting fast forward at random intervals. It did not matter if the file was playing at full screen or in a window -- and my load monitor showed that the processor was not redlining. the file was 400x160 (was widescreen -- with black bars on the top and bottom). I saved the "info" file but not sure who to get that too.

Thor