There are couple of methods to change your Windows 10 product key. If you current product key is detected as pirated key, you can just change to a genuine product key instead of reinstalling the machine.
Compare to previous version of Windows Operating System, Windows 10 more flexible and offers five method for you to update / change Windows Product Key with ease.
Method 1: Slui
1. Click Windows Logo (Start) > type slui > choose slui (with key) as per below screen
Method 3: System > About
1. Click Windows Logo > Settings > System
2. About > Change product key or upgrade your edition of Windows
3. Enter your new product key screen will pop up > Enter your key > Next
2. In Windows Activation column > Change product key
3. Installed product key successfully message will display once the key is changed.