Is your screen totally black? If you shine a bright light, at an angle to the screen, can you see a faint image? If so, then you have a problem with the inverter/back-light. The repair needs to be done by a skilled laptop repair facility. The repair cost is 100 to $150 US.

Have you tried to connect the laptop to an external monitor? Most laptops have a VGA port where you can connect a external monitor. My old Compaq required a Function key be pressed to activate the port. It was Fn + F3. If the laptop works with the external monitor then your problem is in the laptop screen or the cable between the screen and the motherboard. If it doesn't work with the external monitor your problem is with the video circuit on the motherboard. The repair cost is almost the same as buying a NEW computer.

Good Luck