Solved, but via something I've not seen in other posts or when Google searching, so hope this helps others. I made two changes I hadn't seen previously. I don't honestly know if both are required, but doing both resulted in a successful install.
- The downloaded installer extracts to the folder specified in the user's TEMP or TMP environment variable. These are usually set to the AppData\Local\Temp folder in the user profile (i.e., %USERPROFILE%\AppData\Local\Temp). I'm not sure why, perhaps something in later versions of Windows, but installing from this location after the initial extract doesn't work. I created a TEMP folder off the root of my primary disk drive (C:\Temp). The new folder has different security settings than the default temp folder, which may be the issue and suggests an alternative solution. In any case, attempting to install from the downloaded exe after changing the TEMP and TMP user environment variables functioned with anti-virus and firewall turned off, plus doing a selective startup.
- Intuit's instructions for doing a selective startup don't work on later versions of Windows 10 (or, I suspect, Windows 11). Unchecking "Load startup items" via msconfig does not disable startup items (why have the option, Microsoft?). Startup items must be disabled one by one via Task Manager, on the Startup tab. Be careful not to disable items you may need, e.g., touchpad software. Also be sure to make a note of any items already marked "Disabled" so you don't re-enable them after you restore Windows to normal operation.
One thing still puzzles me. In a prior attempt, I ran the extractor, moved what was extracted from the AppData location to C:\Temp, and tried to install, but it failed. In a separate attempt, I correctly disabled startup items using Task Manager and tried to install directly from the downloaded exe without modifying TEMP and TMP, and that also failed. The only theory I can come up with is that Windows prevented something from being extracted to the AppData temp folder, even with anti-virus and firewall disabled. Also, because I eventually configured all the "fixes," I don't know which fix, or which combination of fixes, really resolved the problem.
