I can't reset my hp laptop

How can I reset my hp laptop to default settings? I can't do it by turning it on and pressing f11 because when I do that the screen just goes blank. I'm doing it properly I think cause I repeatedly press f11 as soon as the laptop turns on, and nothing comes up. Is there another way I can reset it, but I can't use a disk because I can't get one at the moment. When I don't press f11 it just comes up with the hp logo and 'please wait' for a few seconds and then it goes blank. I have tried waiting to see if it will do anything and after an hour still nothing had happened