AVI file extensions

assuming you have the newest version of mediaplayer and real player the problem is then that you don't have the correct codecs.
The most commonly used ones are called divx 5.1 which can be found at download.com.
http://tinyurl.com/odgr

here's the quicktime link , in case you wanted that too
http://tinyurl.com/odhc
Leopold

Are your trying to play downloaded movies?

If so, here's the deal. SOME are created drom steaming audio and have corrupted compression.
SOME are just fake files. SOME have European codecs. SOME ????. It's a crap shoot.
If you are using Kazaalite you can download AVIPREVIEW that will also come loaded with codecs.

DIVX is around but not complete with it's codec pack, you may also need the codec packs from others such as Codec Shack (simple search to find it). A company named FMV also makes software to identify FOUR C codes used and determine the codec needed, support is great just don't mention Kazaa.

Good luck,
OM