For info about how to activate Windows 10, see Activation in Windows 10.
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.
If you have a volume license and want to activate Windows by phone, go to Microsoft Volume Licensing Activation Centers Worldwide Telephone Numbers.
If you need to install and activate Microsoft Office, go to Download and install or reinstall Office on your PC or Mac.