Just read a tutorial on how to remove audio from video on Mac and Windows which inform us:
You can also give Windows Movie Maker a try. Here are the concrete steps:
1. Import the video to a new project and add it to timeline;
2. Click on the bit of the video you want to mute;
3. Click on "Clip" at the top of the screen;
4. Click on audio;
5. Click on mute.
This way only mute the audio from video rather than delete the audio from video. Furthermore, if your operating system is Mac or your source files are incompatible with Windows Movie Maker, the way will not work at all.
If you are a Mac user, iMovie is a nice choice to remove sound from video. Here are the concrete steps:
1. Import video to iMovie and place it on the timeline;
2. Select the track in the timeline;
3. Go to "Advanced" tab -> Extract Audio;
4. Select the audio track and delete it.
This way is only for Mac users. If you are using a Windows or your source files are not supported by iMovie, it is not fit you. Since your source file is AVI format, you need to convert them to iMovie supported format.