Use Wavepad. The normal release, unlicensed, is full-featured for a trial period. Click the Get It Free link for a scaled-down version.
- On the Wavepad toolbar, click OPEN and load your file
- Click the EDIT tab
- Click the SPLIT button on the toolbar
- Choose SPLIT INTO COMPONENT CHANNELS
- Choose the Right Channel tab from the three shown below the toolbar
- Click the FILE menu and Save As - to a folder of your choice
- Import that MONO file into Videopad