Quick answer: If Windows 11 is already installed, open Settings → System → Activation → Change product key, enter your 25-character key and select Next. For a new PC or a clean install, download Windows 11 from Microsoft's official download page, install it, then enter the key in the same place.
This guide covers Windows 11 Pro, Windows 11 Home, the Home-to-Pro upgrade key and Windows 11 Enterprise. Enterprise LTSC and IoT LTSC keys use the installation media sent with your order (see the note in Step 2).
Before you start
- Check your PC is compatible. Windows 11 needs a 64-bit CPU with 2+ cores, 4 GB RAM, 64 GB storage, UEFI with Secure Boot and TPM 2.0. Run Microsoft's PC Health Check app or read the official requirements.
- Back up your files to OneDrive or an external drive before a clean install.
- Have your product key ready. It's in your order email: 25 characters in the format XXXXX-XXXXX-XXXXX-XXXXX-XXXXX.
- Match the key to the edition. A Pro key activates Pro, a Home key activates Home. You can't activate Home with a Pro key directly, but you can upgrade (see Step 3).
Step 1: Choose how to get Windows 11
| Your situation | What to do |
|---|---|
| Windows 11 is already installed (Home or Pro) | Skip to Step 3 and just enter the key. No download needed. |
| Upgrading from Windows 10 on the same PC | Use Windows 11 Installation Assistant from Microsoft's download page. Your files and apps are kept. |
| New PC, new drive or clean install | Create a bootable USB with the Media Creation Tool (8 GB+ USB stick). |
| Virtual machine or advanced setup | Download the Windows 11 ISO from the same page. |
All three tools are on microsoft.com/software-download/windows11. The same media installs Home and Pro; the edition is decided by the key you enter. Never download Windows from third-party mirror sites.
Step 2: Install Windows 11 (clean install)
- Run the Media Creation Tool on any working PC, accept the licence terms and choose Create installation media → USB flash drive.
- Plug the USB into the target PC and boot from it (usually F12, F11, Esc or F8 at start-up opens the boot menu).
- Choose your language and select Install now.
- When asked for a product key, enter it now, or select I don't have a product key and activate after setup. If you skip, pick the edition that matches your key (Home or Pro).
- Select Custom: Install Windows only, choose the drive and let setup finish. The PC restarts several times.
- Complete the out-of-box setup. Windows 11 Home needs an internet connection and a Microsoft account to finish.
Enterprise LTSC and IoT Enterprise LTSC: these editions aren't on the public download page. Use the installation link from your order email. Microsoft's Evaluation Center ISOs are time-limited trials and can't be activated with a key, so don't use them for a permanent install.
Step 3: Activate Windows 11 with your product key
- Open Settings → System → Activation.
- Select Change product key. On Home, it's under Upgrade your edition of Windows.
- Enter the 25-character key from your order email and select Next, then Activate.
- Check the Activation page shows "Windows is activated". If you sign in with a Microsoft account, it may say "activated with a digital license linked to your Microsoft account", which makes reactivation after hardware changes easier.
Upgrading Windows 11 Home to Pro
Enter your Pro upgrade key or a full Windows 11 Pro key in Change product key. Windows downloads nothing extra: it unlocks Pro features, restarts once, and keeps all your files and apps. The whole upgrade usually takes under 10 minutes.
Upgrading Pro to Enterprise
Install Windows 11 Pro first, then enter your Enterprise key under Change product key. Windows switches to Enterprise in place without reinstalling.
Activating from the command line
If the Settings page won't accept the key, open Command Prompt as administrator and run:
slmgr /ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXXslmgr /ato
Run slmgr /xpr to confirm the activation status.
Troubleshooting activation
| Problem | Likely cause and fix |
|---|---|
| "This product key didn't work" | Typo or wrong edition. Copy-paste the key, and make sure you're entering a Pro key on Pro (or using Change product key to upgrade from Home). |
| "We can't activate Windows on this device" | No internet or Microsoft's servers are busy. Connect, wait a few minutes and select Activate again. |
| Activated before, not after a motherboard change | Use Troubleshoot on the Activation page and choose "I changed hardware on this device recently" while signed in to your Microsoft account. |
| Phone activation requested | Run slui 4, choose your country and follow the automated prompts. |
Microsoft's own activation help page lists every error code. If you're still stuck, reply to your order email with a screenshot of the Activation page and our support team will help.
Frequently asked questions
Do I need to reinstall Windows to activate it?
No. If Windows 11 is installed and running, entering the key in Settings is enough, even if it was never activated.
Can I use a Windows 11 key on Windows 10?
Windows 11 keys normally activate the matching Windows 10 edition too, but we recommend upgrading to Windows 11 because Windows 10 reached end of support on 14 October 2025.
Is the downloaded Windows 11 the full version?
Yes. Microsoft's media is the full, genuine Windows 11. It runs unactivated with a watermark and limited personalisation until you enter a key.
Where can I find guides for other products?
See all our installation and activation guides, including Office for Windows.
Useful links
| Link | What it's for |
|---|---|
| Windows 11 download (Microsoft) | Installation Assistant, Media Creation Tool and ISO |
| Windows 11 requirements | Hardware compatibility |
| Activate Windows (Microsoft Support) | Activation errors and fixes |
| Windows 11 Pro key | Buy a Windows 11 Pro licence |
| Windows 11 Pro upgrade key | Upgrade Home to Pro |