A required codec isn't available

When i try to open my .avi file it says a required codec isnt available. I have tried downloading perian but that didnt work. I need help!!!

Why not check to see what codec is actually missing? If the file won't open in the QT player, then use the Finder "Info" window or open the file in a player like VLC and check its "Media Information" window. If the file with open in the QT player but not play, then check the "Inspector" window for this information. Remember that the AVI file container has not been officially supported by its creator for more than a decade and many older codecs have never been transcoded for Mac use or updated for OS X systems despite continued common use by many Windows users and those that can be viewed on a Mac may require the QT 7 player for "lagacy" codec playback.

ok now im using perian and it only plays audio and no video. is there still a codec missing?

Only you can tell for sure by checling the "Info" or "Inspector" window for the file and you're not telling us what it says.

Sample File:

QT 7 "Inspector" Window...

"Inspector" Window for QT X Player...

Finder "Get Info" Window for Mac OS X...

VLC "Media Information" Window...

All of these windows say the sample file I opened contains H.264 (JVT/AVC) encoded video and AAC encoded audio. Some even point out that my sample file also contains an inactive AC3 audio track. To know what codecs were used to create the file you are having problems with, you have to check the window for your file on your computer.

what does this mean?

It means your AVI file contains H.264 video and MP3 audio which is normally playable using Perian if the H.264 Profile and Level are within limitation standards. This means you need to use a utility like MediaInfo to read the Profile and Level for the video to ensure it meets JVT (ITU-T H.264 and ISO/IEC MPEG-4 AVC) stantards. If not, then QT will not play it. For instance, the encoded (not plyaback) dimensions and frame rate for this file require a minimum 4.2 Level for playback. Since some users may encode their content using custom settings for playback using media players that can ignore JVT standards, you must actually verify the H.264 Provile and Level before you will know if the file is/should be QT playback compatible.