If you are in any doubt you can follow this very simple step to ensure your Windows is LEGAL:
Open command prompt as an administrator (search “cmd” without quotes in start menu then right click run as administrator. Type slmgr /dli into it and then hit enter.
(you can copy and paste the command from here and press CTRL V to paste in the command line interface)
A little pop up window will then tell you the type of licence you have installed.
If it says VOLUME_MAK then it is not a legitimate licence (It could stop working at any time).
If it says Retail or OEM then you are legal and good to go.
If this helps please drop a comment to say thanks 🙂