It appears that the videos uses the Indeo Video codec developed by Intel, which is not supported by Vista and Win7.
I had the same issue and this is how I fixed it (on Win7):
1. Download the Indeo Video codec from www.filewatcher.com/m/iv5setup.exe.2068266.0.0.html
2. Install the codec as Admin.
3. Start a command prompt as Admin.
4. Navigate to "c:\windows\SysWOW64\" (On a 64-bit system)
5. Execute the following command: regsvr32 ir50_32.dll
6. Start the game and enjoy the sound in the videos!
I found most of this information on this thread: www.moviecodec.com/video-codecs/iv50-codec-477/
Good luck and I hope it works for you as well!
Post edited July 17, 2013 by Reich