Here’s a tip if you need to change your product key in Windows 8. It also works in earlier versions of Windows, but those versions have easier ways of doing it. In Windows 8 you need to use the Windows Software Licensing Management Tool (slmgr.vbs)
- Open a Command Prompt with elevated privileges (from the Windows 8 Start Screen, type cmd, right-click the result, and click ‘Run with Elevated Privileges’ along the bottom.
- Type slmgr –ipk <your product key>
The slmgr tool is a .vbs script that you can use to install product keys, activate, or display licensing activation for Windows. the –ipk switch installs a new product key, either in absence of an existing one, or to replace it.
Assuming you are connected to the Internet, the Activate Windows message will disappear immediately, and you will be able to use features and settings in Windows that are blocked until you activate.
Of course, the best way to not need this trick is to add the proper product key at the installation