I think I figured out the sequence of events - and solved my problem as I was writing this.
- My computer is a 5 y/o Toshiba Satellite laptop with Windows 10 Creators Update, and my system is well maintained and updated. I have no other software problems.
- I installed the Kingsoft WPS PDF to Word Converter, it didn't work for me and I decided to uninstall it.
- I tried PortableApps / Revo Uninstaller to get rid of it, and it crashed trying to run the app's uninstaller.
- The uninstall not only failed, but Revo Uninstaller was gone from PortableApps.
- I figured out that BitDefender was blocking the uninstaller as a potentially malicious app, and believe it's interaction with the uninstall process caused the problems.
- I was finally able to uninstall the WPS PDF to Word app by turning off BitDefender temporarily (I also turned on Windows Defender and Firewall temporarily.)
- Before and after the successful uninstallation of WPS PDF to Word, I was unable to reinstall Revo Unstaller in PortableApps - it stops with the message : "Error opening file for writing"
- After several failed attempts to solve the problem, I simply uninstalled Portableapps on my D: drive (a partition on my laptop hard drive) by deleting the PortableApps directory, and reinstalled the Portable Apps platform and a few utilities.
My experience reaffirmed my appreciation of the PortableApps program - no complex installations, no registry issues, a perfectly clean hard disk after the uninstall / removal of the platform. And a quick and easy re-install of the platform and my apps.