Media Player Classic is a software that can be used to play multimedia on a computer. Some time it may happen that the Media Player Classic is unable to play RMVB extension files. This could be due to the fact that Real Audio decoder is disabled. The user will need to change this setting by accessing the configuration of the K-Lite Codec Pack. After saving the relevant settings there should not be any issues with playing RMVB extension files.
Media Player Classic Home Cinema is not playing RMVB sound extensions under Windows 7; what can be done?
Click on the Start Button > All programs > K-Lite Codec Pack > Configuration > ffdshow audio decoder
In the new window that opens, search for the Real Audio decoder (normally disabled) and set it to "libavcodec".
Click on Apply and then on the OK button
Thanks to coronetti for this tip.