Activating Windows 10 ensures your system is genuine, secure and able to access all features. Whether you’re installing Windows on a new device, upgrading from an older version, or reactivating after a hardware change, this guide walks you through every method — including product keys, digital licences, and activation troubleshooting.

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What Windows 10 Activation Means

Activation confirms that your copy of Windows is legally licensed. Without activation, you may see a watermark (“Activate Windows”), be unable to personalise your desktop, and miss important feature updates.

Windows 10 can be activated in two official ways:

What Is a Windows 10 Digital Licence?

A digital licence (digital entitlement) activates Windows automatically without needing a product key. You might have one if:

• Your device came with Windows 10 preinstalled (OEM licence)
  
• You upgraded for free from Windows 7 or 8
  
• You bought Windows 10 from the Microsoft Store
  
• Your licence is linked to a Microsoft account
  
• You previously activated Windows on this device
  

A digital licence is usually bound to your device hardware and/or your Microsoft account.

What Is a Windows 10 Product Key?

A product key is a 25-character code used to activate Windows (example: XXXXX-XXXXX-XXXXX-XXXXX-XXXXX). You may get it if:

• You purchased a retail copy of Windows 10
  
• Your laptop/PC has a Windows sticker
  
• Your organisation or school issued you a licence
  
• You purchased a digital key from an authorised retailer
  

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How to Check if Windows 10 Is Already Activated

1. Open Settings
   
2. Go to Update & Security
   
3. Select Activation
   

You will see one of the following messages:

• “Windows is activated” – fully activated
  
• “Windows is activated with a digital licence” – linked to device
  
• “Windows is activated with a digital licence linked to your Microsoft account” – ideal for future hardware changes
  
• “Windows is not activated” – activation required
  

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How to Activate Windows 10 With a Product Key

If you have a 25-digit Windows key, follow these steps:

1. Open Settings
   
2. Select Update & Security
   
3. Click Activation
   
4. Choose Change product key
   
5. Enter your 25-digit key
   
6. Click Next and allow Windows to activate online
   

If You Bought Windows Digitally (Microsoft Store)

Your key is found in:

• Microsoft Store order details
  
• Confirmation email
  
• Your Microsoft account > Order history
  

If You Bought a Physical (Retail) Copy

Check:

• Retail card inside the box
  
• USB packaging
  
• Label under the scratch-off area
  

If Your PC Came with Windows Preinstalled (OEM Key)

Your product key may be:

• Embedded in your motherboard (automatic detection)
  
• Printed on the device or packaging
  

Windows usually activates automatically on first boot.

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How to Activate Windows 10 Using a Digital Licence

If Windows detects a digital licence associated with your hardware or account:

1. Connect your device to the internet
   
2. Go to Settings → Update & Security → Activation
   
3. Windows should activate automatically
   

This works if:

• You upgraded from a genuine Windows 7/8
  
• You bought Windows via the Microsoft Store
  
• Your device has Windows preinstalled
  
• Your licence is linked to your Microsoft account
  

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How to Reactivate Windows 10 After a Hardware Change

Replacing your motherboard is the most common cause of lost activation.

To prepare for future changes:

Link Your Licence to Your Microsoft Account

1. Go to Settings → Update & Security → Activation
   
2. Under “Windows is activated with a digital licence”, confirm it says linked to your Microsoft account
   
3. Sign in with your Microsoft account if needed
   

Reactivating After a Hardware Change

1. Go to Settings → Update & Security → Activation
   
2. Click Troubleshoot
   
3. Select I changed hardware on this device recently
   
4. Sign in to your Microsoft account
   
5. Select your device from the list
   
6. Choose This is the device I’m using right now
   
7. Click Activate
   

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Other Activation Methods (Phone Activation)

If online activation fails:

1. Press Windows key + R
   
2. Type: slui 4
   
3. Choose United Kingdom
   
4. Call the free activation number
   
5. Follow the automated instructions
   

This method is still supported for certain licence types.

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How to Fix Common Windows 10 Activation Errors

Here are the most frequent error codes and solutions:

0xC004C003 – Key already used

• Key used on another device
  
• Check purchase source
  
• Use phone activation if valid
  

0xC004F034 – Invalid key

• Mistyped key
  
• Wrong Windows edition (Home vs Pro mismatch)
  

0x803FA067 – Hardware mismatch

• Use activation troubleshooter
  

0xC004C008 – Key overused

• Retail key used too many times
  
• Contact Microsoft support
  

0x8007232B – DNS name does not exist

• Often occurs on enterprise editions
  
• Switch to retail activation method
  

Quick Troubleshooting Checklist

• Verify Home/Pro edition matches the key
  
• Check internet connection
  
• Sign in with your Microsoft account
  
• Use Activation Troubleshooter
  
• Confirm the key is genuine and unused
  

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Where to Buy Genuine Windows 10 Licences (UK)

To ensure your licence is valid and supported:

Official Sources

• Microsoft Store (recommended)
  
• Amazon UK (only from authorised sellers)
  
• Currys PC World
  
• Argos
  

Avoid

• Extremely cheap third-party keys
  
• Unofficial software resellers
  
• “Lifetime keys” at unrealistically low prices
  

These often lead to activation failures.

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Frequently Asked Questions

How do I activate Windows 10 without a product key?

If you have a digital licence, Windows activates automatically.

Is Windows 10 activation still available in 2025+?

Yes. Microsoft still supports Windows 10 activation.

Can you activate Windows 10 for free?

Only if:

• You upgraded from a genuine Windows 7/8
  
• You have a device with a digital licence
  

Otherwise, you must buy a genuine key.

How do I find my product key?

Try:

• Microsoft Store account
  
• Retail box
  
• Sticker on the device
  

Command prompt:

wmic path SoftwareLicensingService get OA3xOriginalProductKey

What happens if Windows 10 is not activated?

• You get a watermark
  
• No personalisation options
  
• Limited access to updates
  

Can I transfer a Windows 10 licence to another PC?

Retail licences = Yes
OEM licences = No

Why is my Windows 10 not activating after reset?

You may need to sign in with your Microsoft account or re-enter your key.

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Final Thoughts

Activating Windows 10 is usually simple — either with a digital licence or a product key. This guide covers all methods, from new installations to hardware-change reactivations and troubleshooting. Follow the steps based on your licence type, and your system should activate quickly and reliably.