The way I fixed this problem ( to me it happened on windows 10) is that i used a bootable usb stick with "DBAN". DBAN (Darik's Boot and Nuke) is like an OS with which you can erase your hard drives. I used DBAN to erase my hard drive clean and then used a bootable Windows 10 usb stick to reinstall Windows. This will erase everything on your computer...but it works. I had no choice, I have tried everything to recover my Windows but with no success before this. Hope this helps.
I have done this on a Lenovo Ideapad 100 15IBD