Why won't my MPEG-2 files play in RealPlayer?

In order for RealPlayer to play MPEG-2 files, you must first install a DirectShow-compatible MPEG-2 decoder on your computer. Most computer DVD playback software includes a DirectShow-compatible MPEG-2 decoder. If you have DVD playback software installed, please try re-installing this software before attempting to playback MPEG-2 content.