Blue screen at start-up on mini net book

Hello,
I have an HP mini net book that I turned on tonite but got a blank blue screen ~~ this happened once before and my friend gave me 2 keys (or3) to hit that brought it back ~~ does anyone know what they are? I already tried the fn f6 and they don't work. I really need this as I have to be at the dr.s office with my Mom tomorrow as she goes thru some testing.