Change Product Key in Windows Server 2012
Windows Server 2012 does not offer a “Change Product Key” link that is commonly found in Windows Server 2008. To change the product key in Windows Server 2012:
1. Open the Start Menu.
2. Type in “Slui.exe 0x3” in the search box.
3. Click the “Slui.exe 0x3” icon.
4. Type in the new product key in the Windows Activation window and click “Activate”.