My laptop won't start

Hello, I've had trouble with my laptop blue 'screening' now for about 4 months, however it always restarted - until now. When I switch the laptop on, it comes up with the two options 'Run Startup Repair (recommended) or 'start windows normally' . Whenever I choose the first option, it stops after a minute or two and says that it cannot determine a problem or a solution, and asks me to shut down my laptop. If I choose to start windows normally, it will begin to load for about 5 seconds, before a blue screen flashes for a millisecond, then restarts. It is a Dell Vostro 1400, anyone know what to do? help!