Download Switch Sound Converter free (See resource link below). Follow the setup and installation instructions to install it.
Launch Switch Sound Converter from your Desktop or the location to which you saved it.
Click "Add files" then locate the AAC sound file you wish to convert. Click "Open" to load it to your program.
Select "MP3" in the output format window, then click "Encoder Options." Change your quality settings, then select "Stereo" for left and right audio playback. Click "OK" to save your changes.
Select the output folder to save your converted file, then click "Convert." When the conversion is done, your AAC audio file becomes an MP3.