AVI is a container. It’s like a wrapper, and inside you can have audio and video streams encoded in various codecs.
To play back an AVI encoded in a specific codec, you need to have the codec installed on your system.
There are tools to identify which codec(s) a media file uses.
Once you find out what codec the file uses (for example video codecs are often identified by their fourcc (four character code)), you can search it on the web.
A clean installation of Windows will not support Quicktime (extension .mov) or mp4 files. The default player for those is QuickTime Player.
As a note aside: you’ll often see a lot of people suggesting you get codec packs. Those are just compilations of codecs people put together. It’s really a toss-up whether they are stable with your system or if they’ll make it crash. I know it’s more tedious to use a diagnostic tool like gspot, and find the codecs on an as-needed basis and download them, but if something goes wrong, you know immediately what caused it and you can uninstall right away. You can’t do that cleanly with codec packs though. If you must get a codec pack (for example because you don’t have much time), I’d suggest ffdshow-tryout, or an all-in-one player like VideoLan. They support lots of formats and tend to be fairly stable. (You could for example use VideoLan as a replacement for WMP or QuickTime Player altogether).
I just got a new computer an it has windows vista. I downloaded a movie from limewire but it wont play. I dont understand i can play mpeg and mpg but not avi or mp4 or mov. i downloaded the Divx converter to fix it but ionno how to use it. Please please help me thank you!
Again im not asking how to download but just how to get my stuff to play its the same when i buy a movie off the web.