I know it plays 3GP files, which are video format for phones, but i'm not sure which other formats it plays, so, you're looking for an Avi to 3GP converter...
This site lists alot -
http://www.mymusictools.com/free/avi...-converter.htm
I'm in the process of seeing if Nokia Multimedia Player can convery... I doubt it but you never know.
Once again my knowledge is limited. Someone else will be along with better suggestions.
EDIT: 2 posts before this one. And it's much more useful.
---------- Post added at 14:26 ---------- Previous post was at 13:54 ----------
Ohh, the link you're wanting is this -
http://www.nurs.or.jp/~calcium/3gpp/...nverter034.zip
when you've extracted and run setup.exe change the language in the lower left hand part of the program from japanese to english.