Install or Replace Windows 8 Serial Key

1. Run  Command Prompt with administrator rights or privileges. To do so, Click on Search and type Cmd then we get Command Prompt Right click it and Click Run as Administrator

2. In the command prompt window, type the following command:
slmgr.vbs -ipk <insert your Serial Key here>


3. To activate windows after changing the key, run the following command in the command prompt window:
slmgr.vbs -ato (Must be connected with internet). And Enjoy.....