I was tempted to use my laptop as a boat anchor but i decided to keep trying because i couldnt afford a new computer. I think if you hold the shift key down when you start the computer it should take you to the boot screen. Youll need to back up your info onto a USB then uninstall and reinstall. Thats how i did it i think.... it was a while ago.
Or you could try this youtube clip
https://www.youtube.com/watch?v=TwIOazT1BxU&autoplay=1
good luck or ring Microsoft.