From Ying Games and Fun:
mp4 to mp3 converter for Windows 8 is a slick tool that extract audio from you mp4 video files. Select multiple mp4 files to start converting. By default mp3 files are stored under libraries - Music. You can optionally change the save folder. To keep the computer responsive, it converts up to two mp4 files at the same time. If there are more files to convert, they will just wait in the queue to finish. All files successfully converted will be in status green. If any error happens in the conversion, those files will be marked as status red.