Can you please let us know what happens when you play MP4 files? Are you able to see the video and hear the audio as well?
In the meanwhile, please follow these steps:
1. Open RealPlayer.
2. Click the RealPlayer logo, then Preferences.
3. In the Category pane, select Hardware.
- Under Video Card Compatibility, move the slider bar to Best Performance.
- Click OK twice to save the changes.
- Close out of RealPlayer, restart it.