Change product key in Windows 8 or in Windows Server 2012
- Swipe in from the right edge of the screen, and then tap Search. Or, if you are using a mouse, point to the lower-right corner of the screen, and then click Search.
- Type cmd in the Search box.
3. Right-click Command Prompt, and then click Run as administrator. If you are prompted for an administrator password or for a confirmation, type the password, or click Allow.
4. Run the following command at the elevated command prompt:
slmgr.vbs /ipk <Your product key>