Hikari

There were an update and when it was done it bringed me back to where I can sign in and everytime I try to sign in it keeps saying The user profile service service failed the sign-in. User profile cannot be loaded. So I don't know what to do. I tried a guest and few other profiles and it says the same thing. I'm on windows 8/8.1 and I cant seem to figure how how to bring up the menu for refreshing your pc as soon as you turn your pc on. I did it before but now I cant figure out what button is it.