Before doing anything else, just as a precaution do a copy of your entire my documents folder by accessing it via C/Users etc.
I think your best option at present is to see if you have a System Restore point still in existence before you did anything Unitronics. If you do, set that underway and see how well it restores things.
If you don't have a restore point back far enough, with Visilogic 9.8.65 installed, use Revo Uninstaller portable ( https://www.revouninstaller.com/download-free-portable.php ) and do a thorough uninstall, as deep as the program lets you run it...go into Options etc. Once done, if you can still find a folder called "Unitronics VisiLogic_C" in program files/Unitronics, delete this. Reboot the puter. See what the behaviour is now.
Once rebooted, install .79 using the right click run as admin method and see how it goes after rebooting after installation. If it works then you are ok. If not, repeat the uninstall instructions above to completely get rid of anything .79 ish. Reboot and install 9.8.65 again using right click/run as admin. Reboot and see.
The object of all of this is to try to completely get rid of any strange references in the system that either program has made. 9.8.65 is stable and should run fine if nothing else is messing with it.