then to Programs and Features
then find the Garmin Express program listed there. Click on its entry there, once. It should be highlighted now.
Then look for the Uninstall button, or perhaps the Uninstall link (depending on your Windows version.)
Click on Uninstall.
Uninstall Garmin Express (it's just a program on your computer, and easily reloaded. It holds no data of yours.)
Restart your computer after that.
Then when restarted, and logged in, re-install Garmin Express as follows:
and (if you have a Windows PC) click on the big blue Download button at center bottom of the page. (If you have an Apple, click on the nearby Download for Mac link.)
And download Garmin Express' installer to your computer, save it, then double-click upon it to install Garmin Express.
Then start the program, Garmin Express.
Does it work now?