I want to wrap up this issue of the installer hanging at Step 1 of 24. I posted that there were 2 reports of this behavior from customers within a couple of days of each other, which is why I suspected the cause might be due to a Windows 10 update. It turned out not to be the case. As I previously posted, one customer determined that it was definitively due to anti-virus software.
I am not 100% sure of the cause for the second customer (but I assume that anti-virus software was the cause). (But I hate to assume, but have no other choice here because the customer has moved on.)
This is what that customer did to get it working (which admittedly is a little strange): He had an older PC that my software was working on, and he was trying to install it on an new PC when he got the "installer hangs" problem. So he manually copied files and folders (NI’s/LabVIEW’s and mine) from the old PC to his new PC but my exe still would not launch run (because it wasn't completely "installed", I'm sure). But then he told me he ran the installer again, and then it worked. The installation completed and my program launched and works correctly. End of story. That's all I know.
My best guess is that the installer might not have had permission to copy files or folders (maybe or maybe not due to anti-virus software) and got stuck. But since it verified that the files were already present, it didn't try to copy them, and was able to complete the installation, registering DLL's etc., which allowed the program to launch and run.
In the several weeks that have passed, we have not had any problems. All I can say is that my LV8.5 programs work just fine on Windows 10 Creator update edition.
Cheers! 