How to Change/Install Windows licence key using CMD – Command Prompt.
Installing licence key and activating windows using command prompt.1. On Start and type CMD and run it as Administrator 2. Type slmgr.vbs /ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXX and press Enter. 3. Then type slmgr.vbs /ato and press Enter to activate the licence key.