Once you have found out the codec thanks to AVIcodec you will be able to download it from Internet and install it. This software doesn't provide any codecs, it only finds out which are being used and as the developer indicates, unless you have the required knowledge, the best idea is always to install a good codec pack to solve the problem that arise with unreadable files.
Usually, programs like AVIcodec are used by professionals or by very advanced users that don't always use standards when it comes to multimedia file coding. Despite this, its purpose can serve more than one user to get out of a tight spot.
Thus, if you have any video file with the AVI extension that your multimedia player can't read, download AVIcode for free and find out exactly which codec has been used.