AVI is not a codec, it's a container format that can contain video or audio coded with pretty much any codec. Matroska Video, MKV, is another (open-source) container format.
DivX and Xvid are both groups of video codecs, the latter being open-source and generally just more cosy (no one likes corporations). DivX and Xvid codecs are usually quite customisable, but are generally considered superior in terms of size and quality ratio, compared to the industry giants:
Window's WMV and Apple's QuickTime, both proprietary video compression formats.
H.264 is not a codec, but a video compression standard. DivX and Xvid both support H.264 (well... some versions of DivX and Xvid.)
There's a lot of confusion out there about this stuff (not surprising considering the confusing filenames of many video files), I hope this post clears things up. Try Wikipedia for further reading
ashepard, sounds like a corrupt file, if you ask me. Probably lost, I'm afraid.