Sometimes when you install upgrade utility the installation might halt because some drivers are blocking the installation from finishing.
To make sure that all drivers that might block here are uninstalled, below operation can be made:
Unplug the Konftel unit.
Uninstall Upgrade utility, if you have more than one you need to uninstall all of them.
Also uninstall all windows driver package starting with Konftel.
Open command prompt in admin mode. Do that by open start menu, type cmd, right click on cmd and select run as administrator.
From command prompt enter this command to list the drivers: 'pnputil –e' and press enter.
Check all drivers with Konftel AB Class.
Delete them like this for example: 'pnputil -d oem79.inf'
Delete all Konftel drivers.
List them again to see that all drivers with Konftel AB is gone.
Restart the computer.
Reinstall Upgrade utility.
Plug the Konftel unit in.