This will not return the product key to a never before activated state.
This will not permanently deactivate the product key number and prevent it from being able to be used to activate
another Windows again later. This only removes the product key from the current computer leaving Windows not activated.
This will not remove the product key from Microsoft activation servers. Microsoft activation servers will still have records of all computers the product key have been activated on.
product key number is permanently tied to the motherboard of the computer it was first activated on. It can only be used to activate Windows on the exact same computer that it was first activated on.
product key number can be used to activate Windows on any computer as long as the product key has been removed from any other computer first.
If you only wanted to change the product key number
instead, then see: How to Change the Product Key Number in Windows 7