ok, get a flashlights and shine at laptop screen, can you make anything out? if yes, your backlight needs to be replaced. if not,
connect an external monitor to your laptop, does external work fine? if yes, your hardware is fine, but the laptop screen has a problem
There's several things that could be wrong:
broken video cable - relatively easy replacement
broken inverter - relatively easy replacement
broken lcd screen - expensive, and probably not worth the money
I don't know of any practical ways to test any of them, but in all cases you will need to take the laptop apart. So, I think you should bring it to a repair shop and have them do it for you.
im really sorry for the Very late response.
well the thing is i press the f12 to go to the menu i can see it fine and all, but when i enter to start system normally the screen just turns black. also i tried the installation cd, i see the reboot from cd. i press enter after that the screen just turns black aswell.