If you have not yet solved your problem, there is one more thing I would like you to try.
1. Type SERVICES in the search box and navigate to the services page.
2. Scroll down to the service called Windows Installer. The startup type should be MANUAL and the service should not be started. If this is so, then that is not the problem. Sorry. But, if the service is started do next steps.
3. Stop the Installer Service. Then set the startup type for it to DISABLED.
4. Reboot your system.
5. Go back into Services and set the startup type to MANUAL.
Then see if you can proceed as you planned.
Let us know