if (mp != null)
{
    if (mp.isPlaying())
    {
       mp.stop();
    }
    if (mp != null) mp.release();
    if (mp != null) mp = null;
}

mp = MediaPlayer.create(this, R.raw.sound);

if (mp !=null)
{
   mp.setOnPreparedListener(new MediaPlayer.OnPreparedListener()
   {
      public void onPrepared(MediaPlayer mp)
      {
    if (mp != null) mp.start();
      }
   };
 }
 else
 {
    // error, what should I do here to recover from this situation?
 }

AssetFileDescriptor afd = getResources().openRawResourceFd(R.raw.sound);

//Resets the MediaPlayer state but keeps the resources
mp.reset();

//Sets the data source to the requested sound (R.raw.sound)
mp.setDataSource(afd.getFileDescriptor());

//Prepare the MediaPlayer to play and then start
mp.prepare();
mp.start();