The product key can be removed from the registry by executing a simple command. If you are interested, follow the below mentioned steps to delete Windows product key from registry.
1. Open the Command Prompt with admin rights. To do this, type CMD in Start menu search box and hit Ctrl + Shift + Enter. Or, navigate to Start menu, All Programs, Accessories to find the Command Prompt entry. Right-click on Command Prompt and select Run as administrator option to run it with admin rights.
2. In the Command Prompt window, enter the below mentioned command and hit Enter key.
slmgr -cpky
3. Wait till you see ¡°Product key from registry cleared successfully¡± message.
4. You have just deleted the Windows product key from registry.