This guide covers activating a Windows 10 Pro licence key bought from license4u.co, whether you already have Windows 10 installed or are doing a clean install.
Option A: activate an existing Windows 10 install
- Open Settings > System > About and confirm the edition is Windows 10 Pro (or Home, which this key will upgrade to Pro).
- Go to Settings > Update & Security > Activation and click Change product key.
- Enter the 25-character key from your email and click Next. Activation completes online.
Option B: clean install
- Download the Windows 10 Media Creation Tool from Microsoft's Windows 10 download page and create a bootable USB. Choose 64-bit unless your hardware is 32-bit only.
- Boot from the USB, pick Windows 10 Pro as the edition, and enter your key when prompted or add it later under Activation.
- Complete setup and connect to the internet; Windows activates automatically.
If activation fails
Confirm the edition under About; Pro keys reject Home Single Language, Education and Enterprise installs. Then try slmgr /ipk YOUR-KEY and slmgr /ato in an administrator Command Prompt. If an error code remains, email support@license4u.co with your order number and a screenshot.
Buy the licence here: Windows 10 Pro.