Ok so it installed, AND works!!
Notes:
- I have updated XT-3 FW to 4.0, and downloaded the Webcam software 2.0. It did not fully install the first time, same error.
- I downloaded and installed MS Visual C libraries from link, but did the x64 version (because I thought, yeah, that's what my system is), and Webcam installer gave same error. - I downloaded and installed MS Visual C libraries x86, and Fujifilm Webcam 2.0 then installed with no errors. Restarted and it works.
Super happy I can now use this on my main desktop system, and also pleased with the new Fujifilm X Webcam 2.0 camera controls! I love all the options.