If you need to change the product key of the installed OS, for example. suppose you have installed Windows 10 initially with a generic key, and then wish to change it to an authentic key that you purchased, this can be done quickly without reinstalling. You don't need any third party tools or complex Registry tweaks. Note: This trick also works in Windows 8.1, Windows 8, Windows 7 and Windows Vista. Follow the steps below.
Change the product key in Windows 10
- Open an elevated command prompt. See: How to open elevated command prompt in Windows 10.
- Type the following command to install a new product key and press Enter:
slmgr.vbs -ipk 11111-11111-11111-11111-11111
- To activate Windows after changing the key, you need to run the following command:
Wait for a few seconds and the check System Properties window in Control Panel\System and Security\System. It should say that Windows 10 is activated.