After I click "Automatically close the applications, I get this error: Setup was unable to automatically close all the applications. It is recommended that you close all applications using files that need to be updated by Setup before continuing.
It seems you launched the installer with FSX still running, before the Couatl.exe was able to be shutdown by FSX shutting down. The installer tries to shut down too, but it doesn't always work.
A reinstall after a Windows reboot will surely fix this.
