Windows 7 and 8--->Windows 10 is still free!
Before you start commenting "We know about the assistive technology methods, stop reposting this", its not that method. I had trouble upgrading using that method, so I thought to flip with it, I'm gonna install Windows 10 and see if my windows 7 key works. And it did! but to make sure you use the correct key, download Produkey, which tells you your windows activation key if it is activated, write it down (or take a picture, it is 2016) and type that in in the Windows 10 setup. DISCLAIMER: BACKUP YOUR DRIVES BEFORE DOING THIS, IVE ONLY TRIED THIS ON ONE PC IT MAY NOT WORK ON YOURS