Windows 8 requires an online activation with Microsoft before every features is available to you. If you're installing Windows yourself or upgrading your PC's hardware, you have to re-activate Windows. Some hidden options can be launched via the Run dialog.

Activation 101

You may need to reactivate Windows 8 after upgrading your PC's hardware.

Windows detects changes to the motherboard, hard disk, CPU, and other system components. It deactivates itself after noticing a few too many changes -- in that case you have to re-activate it afterwards.

We covered this when we looked at how to make a Windows 7 PC genuine again -- a de-activated Windows installation may be considered "non-genuine" if there's a problem with the product key.

If you're installing Windows 8 from scratch, you'll need to activate Windows yourself. You may also have to reactivate Windows if Microsoft discovers your key is pirated or in-use on multiple PCs. This system is designed to ensure you're using a legitimate Windows license and that you're not using it on many different PCs.

Reactivating Windows requires a legitimate key. You're allowed to upgrade your PC's hardware and you're also allowed to install your Windows license on a new computer as long as you've removed it from previous computers first. These actions will prevent automatic activation, so you may need to call a Microsoft representative on the phone.

How to Activate Windows

You can activate Windows from the PC settings app. Press Windows Key + C or swipe in from the right to open the charms bar, tap Settings, and tap Change PC settings.

You'll see an Activate Windows option here if Windows isn't yet activated. You can also navigate to PC and devices > PC info to see whether Windows is activated.

Use the Activate button to attempt to automatically activate your Windows installation with Microsoft over the Internet. If an error is preventing Windows from activating, you can see more information about it here. Perform a web search for your specific error message if you need to find more specific information.

If you can't activate Windows online, you can call Microsoft and activate by phone. You'll be asked to provide information and explain your situation. For example, if you've upgraded your hardware and Windows is no longer activating, describe what you've done when they ask. They'll provide you with a code you can enter on your PC to re-activate Windows.

If you don't see the activate by phone option, you can skip directly to it. Press Windows Key + R to open the Run dialog. Type Slui 4 into the Run dialog and press Enter.

Choose your country and Microsoft will provide you with a local phone number and an installation ID. Call the phone number and provide your installation ID.

This process is normally automated, but you'll be able to talk to a Microsoft customer service agent if you need to.

How to Change Your Product Key

You may need to change your installed Windows product key in some cases.

Use the Change product key button on the PC info pane to enter a new product key for Windows. You'll be able to activate Windows normally afterwards.

This button may not always appear. If you can't change the product key from here, take the command route. Press Windows Key + R to open the Run dialog, type Slui 3 into the Run dialog, and press Enter.

Enter your new product key. You can activate Windows normally afterwards.

Most Windows Users Won't Need to Do This

This isn't something most Windows users will have to deal with. You'll usually only need to activate Windows yourself if you install your own copy of Windows or upgrade your PC's hardware. This should be fairly easy -- even if the activation process is failing, you can talk to a customer support agent and have them activate Windows for you.

There are third-party tools that attempt to bypass Windows activation available online. You shouldn't use these. These tools are against the license agreement, could break as Microsoft introduces new updates to Windows, and may include malware if you download them from shady file-sharing sites.

Do you have any experience with Windows activation, or any tips for navigating the activation-by-phone system? Leave a comment and share them!

Image Credit: Karl Baron on Flickr