Activate Windows 7 or Windows 8.1
Activation helps verify that your copy of Windows is genuine and hasn’t been used on more devices than the Microsoft Software License Terms allow.

A Windows product key is a 25-character code used to activate Windows 7 or Windows 8.1. It looks like this:

PRODUCT KEY: XXXXX-XXXXX-XXXXX-XXXXX-XXXXX

Without a product key, you won't be able to activate your device.

Your product key should be in the confirmation email you received after buying Windows, included with the packaging that came with your PC, or on the Certificate of Authenticity (COA) attached to the back or bottom of your PC.

For more info about Windows product keys and where to find them for the copy of Windows that’s on your PC, see Find your Windows product key.
Try the Activation troubleshooter
If you're running Windows 10, version 1607 or later, the Activation troubleshooter might help reactivate Windows if you recently made a significant hardware change (such as replacing the motherboard) or reinstalled Windows. Fix common errors
The following are some of the most common activation errors with possible solutions for Windows 10. If you're getting an error code that isn't listed on this page, contact customer support.

If you upgraded to Windows 10 for free and your device isn’t activated, make sure you’re running the latest version of Windows 10. This version includes improvements to activation and troubleshooting activation errors. For more info about how to keep Windows up to date, see WindowsIf you're having trouble activating Windows 10, follow these steps to fix activation errors:

Confirm that your device is up to date and running Windows 10, version 1607 or later. In the search box on the taskbar, type winver, and then select Winver from the list of results. You'll see the version and build of Windows.
Not running Windows 10, version 1607 or later? Learn how to update your device at0xC004C060, 0xC004C4A2, 0xC004C4A2, 0x803FA067L, 0xC004C001, 0xC004C004, 0xC004F004, 0xC004C007, 0xC004F005, 0xC004C00F, 0xC004C010, 0xC004C00E, 0xC004C4A4, 0xC004C4A5, 0xC004B001, 0xC004F010, 0xC004F050 ou entered a product key that can't be used to activate Windows. Enter a different product key or buy a new product key.You upgraded to Windows 10, but the activation servers were busy. If you upgraded from an activated copy of Windows 7 or Windows 8.1, your copy of Windows 10 will be automatically activated, or you can wait a while and then select Activate. If you continue to have problems with activation,You upgraded to Windows 10 using the free upgrade offer, but Windows 10 isn't activated after a reinstall. Your copy of Windows 10 should automatically be activated as long as you didn't make any significant hardware changes to your device (such as replacing the motherboard). If you continue to have problems with activation, contact