If you have a Windows 10 refurbished PC purchase and it is asking to be activated after you get into Windows, it can be easily activated by using the product code located on the PC itself.
Here is how to locate and activate your product key:
1. First, locate the Windows 10 product key sticker on the computer. On a laptop, this would typically be on the bottom, or perhaps even under the battery if it is removable. For a desktop, it would be on one of the sides of the case or on the top. You will find a multi-colored sticker that may say 'Windows 10' or 'Windows 10 for Refurbs'. Some of the key will be covered for security reasons. The full key will need to be revealed. On this sticker, gently scratch off the grey/silver Microsoft portion with a coin to reveal the full product key.
2. To activate this key on your Windows 10 system, right click on the Start button, typically found at the lower left corner of the screen and from the list of options, choose Settings.
3. From the Windows Settings page, from the list of categories, click on the Update & Security option.
4. Select Activation on the menu on the left side of Settings.
5. Click on Change Product Key on the Activation window.
6. On the Enter a Product Key window, type in the key from the product key sticker. Entering dashes will be done automatically so do not include those after each set of letters and numbers. You should have a total of 25 characters. If you have less than that, double check that you scratched off all the silver material.
7. Click Next to complete activation and you're all set!