Then last week I accidentally stumbled upon the solution to my problem. I had noticed that occasionally when I tried to watch a YouTube video, there would be no sound. For some reason, if I opened the sound settings window, the sound would work. So I just started leaving the window open if I had trouble with the sound while watching videos. Then I noticed that there was a drop down menu titled "Choose you output device". There were three choices, "Speakers (Turtle Beach Riviera Wave", "Digital Output (Turtle Beach Riviera Wave" and "Digital Audio (S/PDIF) (High Definition Audio Device)".
It had been set on the "Speakers" option and so I tried the "Digital Output" setting. Bingo! The sound worked without leaving the window open. I tried the 1965 mod and the engine sounds worked.
I am relating this to close out the issue in the hope that it will help others who may have had that problem. In the meantime, I'm back to driving GPL and installing the remaining mods to get me back to where I was two years ago when I upgraded to Windows 7 (then Windows 10).
Edited by robwmack, Sep 23 2018 - 08:19 PM.