Can you get to BIOS? Can you get to boot menu? Safe mode?
Have you tried recovery CD?
if your screen doesn't work at all. have you tried an external monitor? if not, try it. if external doesn't work you got a hardware problem inside the laptop that will need in-depth diagnostic. if external works, get a bright light, with computer running shine it at the screen, if you can see something you laptop backlight needs to be replaced (fairly simple procedure) if you can't see anything at all, further diagnostic required to determine if it's wiring or LCD fault, then replacement naturally.