I have an Asus republic of gamers nvidia Geoforce GTX core i7. I have had this computer for many years. Originally it had windows 8 but has upgraded to windows 10. It has been working perfectly fine until this morning. I started up the laptop but immediately went into windows 7 startup repair mode. I have looked through various sources online on how to fix it, but none of them work. One which involves me on how to switch back to Windows 10 but it doesn't even appear as an option. Its like it doesnt exist. Please I need help?