DVD problems with WS2

I am begining to go brain dead with this problem so I hope you can help. I have created a video production in MSP7. When complete I created a PAL DVD mpeg file. I have imported this file into WS2 and have created a DVD menu. The first menu has text options to 'select audio', 'select subtitles', 'select scenes' or 'play video'. Each option goes to a subsequent menu. 'Select audio' goes to a menu with two options, 'original sound' and 'music' and returns to the main menu. 'Select subtitles' goes to a menu with two options, 'subtitles' or 'no subtitles'. In the Finish step in WS2 when I play the DVD all seems o.k. In the audio menu, if I select 'music'(track 2)and play the video I get both the sound of the original video file, (talking etc.) and the background music.
When I play the file on the computer using Windows Media Player or similar, If I select 'music' and play the video I only get the music and have lost the original sound of the video file.
When I burn the DVD and play in a DVD player I have a number of unusual happenings. Firstly when I select 'music' I again lose the original soundtrack. If I select the original track 1 I lose the background music. Why do both the audio tracks play in WS2 but only one or other in a desktop player? Can I not play more than one audio track at the same time, if so how do I do this? Now for the really strange bit. In the desktop player I find the following. Sometimes (indeed most of the time but not always) when I go to the 'select audio' menu or the 'select subtitle' menu and make a selection it switches off the DVD player. There a a couple of other odd bits, but to keep it fairly simple my main question is this. When I author a DVD in WS2 can I play a second audio track and still retain the audio of the mpeg file created in MSP7? Both tracks seem to play in the Finish Step in WS2 but only one or other in a desktop player or in Windows Media Player. I hope this makes some sort of sense and I would appreciate any help and comments. Thanks BobH.
P.S. My wife suggested our DVD player might be getting senile as it is a few years old. However it plays all other DVDs I have created in WS1 and now WS2 without any problems.