I use a lenovo G-50-80 laptop. It came with Win 8.1 pre-installed. I partitioned it and added Ubuntu and use the PC in dualboot. It upgraded to Win 10 a week ago. I haven't had any problems with that till yesterday when my keyboard stopped working in the login screen of Win 10. I can use my mouse, but so far clicking anything impossible. Keyboard functions like Locking the touchpad and increasing the brightness work, but I am unable to login. The keyboard works fine in Ubuntu and the boot managers (Win and grub2), so I don't think that's a hardware problem. How can I get windows up and running again? Even if re-installation is needed, can I do it without a product key and still not get into any problem? But first, please suggest any 'soft' methods to make the keyboard work again.
And yes, I tried turning it off and back on.