You want to convert the language of the lecture? Or do you want to convert the format of the lecture so that it can play on both cd players and dvd players?
Are these lectures both video and audio, or are they just audio?
Converting the language used in the lectures is beyond my knowledge, at least using software in computers. Converting the format is much easier, depending on what you are starting with. It might help to know the file extension on the lectures...examine them with a free program called MediaInfo, and tell us the results.