This guide covers activating a Windows 11 Pro licence key bought from license4u.co, whether you already have Windows 11 installed or are doing a clean install.
Option A: activate an existing Windows 11 install
- Open Settings > System > About and confirm the edition reads Windows 11 Pro. If it says Home, the key will still work: it upgrades the edition in place.
- Go to Settings > System > Activation and click Change product key.
- Enter the 25-character key from your email and click Next. Activation completes over the internet in under a minute.
Option B: clean install
- Download the official Windows 11 media from Microsoft's Windows 11 download page and create a bootable USB with the Media Creation Tool.
- Boot from the USB, choose Windows 11 Pro when asked for an edition, and enter your key when prompted (or choose "I don't have a product key" and add it later under Activation).
- Finish setup and connect to the internet; Windows activates automatically.
If activation fails
Error 0xC004F050 or "this key didn't work" almost always means the installed edition does not match the key: Pro keys will not activate Home Single Language, Education or Enterprise. Check About first, then run slmgr /ipk YOUR-KEY followed by slmgr /ato from an administrator Command Prompt. Still stuck? Email support@license4u.co with your order number and a screenshot of the error.
Buy the licence here: Windows 11 Pro.