You can use the Mute Video tool to mute the audio of your video.

1. First select Mute Video in the Quick Tools section.

   A dialogue box will be shown to select your input video.

2. The play button will show you how the video will be without sound as preview.

3. If you’re happy with it, select Save video.

4. Select output movie settings, then press OK.

5. Next, choose the location of the output video file.

6. After HD Movie Maker finished processing, you can view the output video.