First to the post from "idisk.mac.com" HUH??

Second, quicktime can play files that use the .AVI wrapper. It is not the wrapper that causes the incompatibility.

It is the intolerable need for users of Windows machines to encode everything using Microsoft's Windows Media Video Codecs.

If they just used a more open Codec the files would run fine in any player that supported the wrapper.

Windows Media Player 9 for Mac does not even support all the Windows Media Codecs.

As for getting all AVI files to open in VLC. On OSX:

Select the file.

Press Command ( the Key with the Apple On it ), I.

This will open the Get Info window.

Goto the section Marked Open With.
If all you see there are the words "Open with:" with a triangle next to it click the triangle to expand it.

select VLC from the pop up menu. then click on the button marked "Change All..."

It will pop up a dialog box to confirm that choice and from that point on you will be able to open these files in VLC by double clicking.