You may require sometimes to remove the license from a Windows installation, whatever this is to re-assign a license to another machine, or before publishing an appliance, etc.
Follow this procedure to put back your Windows installation to the original installation state, license wise.
The following commands need to be performed with the Command Prompt or PowerShell terminal with elevated privileges.
1. Uninstall the product key and unlicense Windows :
slmgr /upk
2. Remove the product key from the registry :
slmgr /cpky
3. Reset the activation timer :
slmgr /rearm
Following these steps, all license trace and activation will be gone.