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.
When installing Windows 10, the digital license associates itself with your device's hardware. If you make significant hardware changes on your device, such as replacing your motherboard, Windows will no longer find a license that matches your device, and you’ll need to reactivate Windows to get it up and running.
To activate Windows, you'll need either a digital license or a product key. To find out which you need, see "What activation method do I use, product key or digital license?" in Activate Windows 10. Then, use the following info to help you successfully prepare for a hardware change and reactivate Windows 10.
Prepare your Windows 10 device for a hardware change
First, follow these steps to find out if Windows 10 is already activated.
Select the Start button, then select Settings > Update & Security > Activation .
If you're not activated, complete the activation process with the steps you see on the Activation page. If you experience an error while activating, see Get help with Windows activation errors.
Once you've confirmed that Windows 10 is activated, follow these steps:
For more info about product keys and digital licenses, see Activate Windows 10.
If you don't have a digital license or product key
If you don't have a product key or digital license, you can purchase a Windows 10 digital license after installation finishes. Follow these steps to make a purchase:
Select the Start button, then select Settings > Update & Security > Activation . Then select Go to Store to go to the Microsoft Store app where you can purchase a Windows 10 digital license.