Many a times, users prefer to download the OS directly from the internet without actually purchasing it or even if they do, they happen to unfortunately lose the product key. Product key is basically the license which provides you the authority to activate the windows OS after installing it. Now whenever you purchase or download the operating system which here in case is Windows 10 always comes with a product key. Concerning the operating systems we deal with, Windows 10 is the last one Microsoft has launched in the market. If you have been using Microsoft products for quite a long time especially its operating system which come under the title WINDOWS, then you must be aware of the development it has brought about in the recent times.