Windows 10 licenses can be pretty expensive (100-200$ per pc), but if you have your old pc which includes a licensed windows 10 you can deactivate it and use the same license for the new one by following these simple steps.
Locating the license:
If you don’t have the license written somewhere, you can check the product box, receipt, check the computer case, If you can’t find it you can use a free software called Nirsoft-ProduKey.
Then open the downloaded software, there you can find the product key. Save it somewhere easy to find.
Deactivating the old PC:
Open Start and type cmd, then right click cmd from the result and select Run as administrator.
The command-prompt window will now open and in there you need to type slmgr.vbs /upk and press enter key and then restart the computer.
After the computer has restarted you should see that your OS is not activated anymore, if you are planning on giving away the machine, it’s recommended to delete the key from the registry as well, is not necessary to deactivate, but it’s a good idea to protect your key.
To do so you follow the steps again but the command now is slmgr.vbs /cpky.
Activating the new machine:
Using the command prompt(cmd) again type in the code slmgr.vbs /ipk #####-#####-#####-#####-##### where the ,,#” are replaced with your key
Now you should see that your machine is fully activated
If you have an old Windows 8 PC you can also de-activate it and use the Windows 8 key to activate Windows 10, for windows 10 also activate with Windows 8 key.