On the system that I upgraded from Windows 8.1 to Windows 10, I successfully installed Start 10, but it will not let me get past the registration window. I can't begin the trial period, enter a product key, or buy a key. The window with those options opens but is completely unresponsive. I've tried restarting my computer, uninstalling Start10 and reinstalling it, etc, but I can never get past the registration window. The same thing happens even when I try to reinstall my licensed copy of Start8. I had used Start8 previously on this system before an in-place upgrade to Windows 10.

However, on a separate, fresh install of Windows 10, the problem does not happen. I could start the trial period for Start10.

Any help would be appreciated. I don't want to do a clean install for my main system.