If you see error code 0x803F7001, it means that a valid license couldn’t be found to activate Windows on your PC. Here's how to activate Windows:
Select the Start button, then select Settings > Update & security > Activation.
If you have a valid product key, select Change product key, and then enter the 25-character product key. If you don’t have a valid product key, select Go to Store, and follow the instructions to buy a license for Windows.
Note: 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 activation errors, see Get help with Windows 10 activation errors.
Article ID: 4026185 - Last Review: 11-Aug-2017 - Revision: 1