Thanks for the information you've prodivded so far.
Please type cmd in the search on the taskbar. Don't press enter key yet. Instead, choose "run as administrator" to launch Command Prompt.
Run these commands one at at time
slmgr /ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXX
(replace the Xs with the actual key)
slmgr /ato