Acer Aspire 5736Z-4801 Switches on but won't start up

When I try to switch my laptop on at failure to start message keeps coming up. It gives me the option to launch a start up repair but when I do it doesn't help, I still can't get past the start up to log on. I'm in the middle of uni exams and really need to get on my laptop. Anyone know how I can fix this quick?