This question already has an answer here:
I have deleted Ubuntu from my PC. When I restart my PC an error occurs that is Grub Rescue. I already run set command. Now I just want to install Windows 10. My PC does not allow me to start installation process. i already follow the instruction given in the reference link. My PC not start boot setup even selection from boot setting. its give me grub rescue command screen. I have tried all possible solution from internet fro example setting of prefix and repair from boot setup etc.....hop my comment will explain my problem.