The audio may not return back to internal speaker when disconnecting the secondary display or unplug the HDMI cable while Windows Media Player is playing a video

When you try to extend or duplicate the desktop to a secondary display by HDMI cable while Windows Media Player is playing media content on the primary display, the audio might also be switched from internal speaker to HDMI output. On windows 7, when you disconnect the secondary display or unplug the HDMI cable, you may experience the following symptom on some devices: The video continues to play, but there is no audio. For other applications in the system, the audio is normal and can be outputted by internal speaker.