Hi there!
I'm Louie, a Microsoft Community member and a fellow Windows 10 user like you. Hope you're doing well and safe there.
I suggest you to follow the below steps and check if it helps.
Click on Start menu, and look for Forza Horizon 4. Right click on it and select Uninstall.
You can also uninstall the game through settings by following the below steps.
- Press Windows key + I together to open Settings.
- Click on Apps > Apps & features.
- Click on Forza Horizon 4.
- Select Uninstall.
You can also do this steps:
Open the Start Menu.
Search for “add or remove programs“.
Click on the search result titled Add or remove programs.
Look through the list of programs installed on your computer and locate and right-click on the program you want to uninstall.
Click on Uninstall in the resulting context menu.
Go through the uninstallation utility by following the onscreen instructions, and the program will be uninstalled.
Here's another thing you can try:
Press the Windows Logo key + R to open a Run dialog.
Type msconfig into the Run dialog and press Enter to launch the System Configuration utility.
Navigate to the Boot tab of the System Configuration utility.
Enable the Safe boot option under the Boot options section by checking the checkbox located directly beside it.
Click on Apply and then on OK.
Click on Restart in the dialog box that pops up to immediately restart your computer.
When the computer boots up, it will be in Safe Mode. While the computer is in Safe Mode, use either set of steps listed and described at the very beginning of this guide to try and uninstall the target application from your computer and check to see if the uninstallation succeeds.
Hope this information helps.
Sincerely,
Louie