There can be a number of reasons why a DVD that you insert does not work. Most audio files are in a compressed form that requires a program and device capable of decoding the digital data stream. The player that your system is using may not be of the latest type. In this case it may not be able to find the codec related to the audio file. If the DVD has been created by ripping music it may be possible that the files require a related codec to function properly which the DVD player is having difficulty in locating. The DVD player may have got damaged due to any of a number of reasons and this may be causing it difficulties in reading CDs that are less than perfect.