If you updated from Win 7 to Win 10:
The first thing you need to do is back up your .tax2017 and .tax2018 files. (and any other tax year files too.) By default, they're located in the documents/turbotax directory. Now it's very common when doing an operating system upgrade from one windows version to another, for all your .tax20nn files to end up in the recycle bin. So you may need to restore those files from the recycle bin before you can back them up.
Next, go straight to the more advanced uninstall procedure at https://ttlc.intuit.com/questions/1901054 and select the one for "Alternate Solution for TurboTax Download". Don't waste your time with the first solution, as chances are it won't work since you upgraded from Win 7.
Finally, if you know how to navigate the registry, run regedt32.exe and delete the following registry values.
\HKEY_CURRENT_USER\Software\Intuit\TurboTax
\HKEY_CURRENT_USER\Software\Intuit\TurboTax 2018
At this point, you must reboot the computer.
Next, you need to run Windows Update until you get no more updates. You must be on Windows 10 version 1809 or newer.
Finally, just to "be sure", reboot the computer again, allow things to "settle down" for a few minutes after you log in. Then run the install program as administrator. To run as administrator, right-click the installation/setup file and select the "run as administrator" option.
