The problem with sound working on your PC but not working on your DVD player is probably caused by the fact that your DVD player does not understand the format of the sound stream in the video files. With GSpot or AVIcodec you can find out which audio codec(s) it is that your DVD player does not support. You need to find an application that you will allow you to transcode the audio streams into a different audio format that IS supported by your DVD player, look here.
Another thing to find out is if your DVD player can be upgraded to a newer firmware version. This could also fix problems like these.
I have just recently began downloading movies(avi format) from bittorrent and burning them to DVD with Windows DVD Maker. 99% of the time the movies burn to the DVD as they should and work perfectly. However, on rare occasions such as when attempting to burn the movie Unstoppable the video of the movie plays great but there is not any sound. The movie plays great from the hard drive, but once burned to the DVD it has no sound. Any advice would be helpful. Keep in mind all these movies are downloads so I did not rip them myself.