This is an attempt to help the stores to do a full reinstall of a computer.
First you need to make sure all important files are saved on Sharepoint/OneDrive.
Then proceed to these guides. (some of the steps are not here, you will also need to follow the instructions on the screen yourself)
Download Teamviewer (will just download the program to your download folder)
If the computer are used by more than one person, you might want to setup another personal account.
Add local account in Windows 10 - Support - Support.kvik.com
Then you need to follow steps 5-8 again on the new account.
Links you might need to save as bookmarks in the browser: