I'd probably go for a repair install which won't affect your personal stuff or installed programs.
If you don't have Win 10 install media then you can create it on either a DVD or USB after reading the instructions at
https://www.microsoft.com/en-gb/software-download/windows10You probably know how to do this, but I'll go through it anyway.
With the machine booted up, open Windows Explorer - This PC - insert the install media and double click on its drive.
This will start the process if using a DVD but will open to its files when using an USB where you will then need to double click on setup Application.
This takes a little over 3hrs on mine and can reset any apps you may have changed back to default.
When done, ensure System Protection is still turned on.