I had the same problem with trying to install Vopt 9.21 on a Windows 10 Pro x64 system. So, I decided to download the Vopt installer from MajorGeeks website, since the Golden Bow Systems website is gone.
I saw the installer file from MajorGeeks was named Vopt921.exe. So, just on a hunch, I renamed the Vopt.exe file I downloaded from SharewareOnsale to Vopt921.exe. I tried the install again and it went off without a hitch. It’s a very simple fix, but it was easily missed by the provider. Which begs the question, “Why did they change the installer file name anyway?” Go figure. :-) Enjoy!