You must install Powerpoint Viewer 1997 as later versions will not support the Sound.  Click on the following 2 links one after the other to install.  If you have high speed you can Save to disk vs. Open. 

aaaaaa/ppview97.exe (save, install)

PowerPoint Presentation (right-click, open, select from a list, choose PPV 97 then choose Slide Show - View across the top)

Note: If a slide appears without a picture, hit the spacebar once. (typical Microsoft bug)

Let me know if it works with sound for you please.

PowerPoint Presentation (after installing PPV 97 from above - right-click, open not save, select from a list, choose PPV 97 then Slide Show-View across the top)