Just starting to use Adobe After fx CS4
Sometimes I here no sound when I play the imported AVI file, and when I render it after adding an effect I get an error message about...some audio settings in the computer ( a hp dm3Notebook) after I export it as rendered AVI, there is also no sound
... what do I need to do to make Win7 work with
The simplest solution is to transcode the offending AVIs to another format. AVI (like MOV) is a wrapper format (rather than a codec) so they can be made with any one of very many different codecs, some of whihc are proprietary codecs or simply uncommon. It sounds like you have some AVIs that use an audio codec that you don't have installed on your machine or that have "muxed" audio (the video and auido data are combined in one channel instead of separate).
[Joseph Dezordi] "I have never understood what is meant by 'AVI is a wrapper'"
It means it is a file format/extension only so any one of very many codecs can be wrapped inside an AVI file (same as an MOV). You see people point that out a lot because it is important to know the codec you're working with, not just the file type ... especially when trying to diagnose problems.
[Joseph Dezordi] "I thought AVI meant uncompressed captured video"
That is not accurate at all ... and AVI can be compressed or uncompressed ... as mentioned above, it's all about the codec.
[Joseph Dezordi] "the offending file is actually an mpg"
There are many kinds of MPEGs ... MPG1, MPG2, MP3, MPG4 ... and some kinds frequently contain muxed audio.
Sorry I can't be more help, but it'll be very difficult for anyone to help you without being able to understand what the issue is since you seem to be describing it using incorrect terms and/or using terms interchangeably when they mean different things. Perhaps it'll benefit you well beyond the current issue you're having to Google "video codecs" and read enough to get at least a general understanding of the most common video codecs.
I just created this account to write what I found to be one possible cause of the problem. Actually I was looking possible solutions to the same problem (no audio at the final AVI file) but I couldn't find anything, specially after reading about having to know which codec the original video has...bla bla)
The cause was a mistake of mine: by default, when adding a composition to the processing queue, there are some settings by default. When clicking the "Exit module" option, I found that by default the check box for including the audio was unchecked! So just click on it, choose some random codec and voila!
I know this is not the solution for most of the serious audio problems, but I think it is worth to write this experience in case some else could use it.