To change the licence key and activate Windows:

1. Login to the server and run an Administrator command prompt.
2. Type the following replacing the text with your MAK key to setup the key.
   

   slmgr.vbs /ipk <MAK>

    
3. To activate windows run the following command
   

   slmgr.vbs /ato

    
4. Windows should now be using the new MAK be activated over the internet.