LCD brightness troubles- only visable with 2 spotlights

Hi,
I have an inspiron8600 with a Geforce go 5650 video card.
Now I am facing some problem.

The display is black, the only way I can see at least something is to place spot lights in front of screen, and then it is still hard to see. If I change graphic settings it becomes normal bright for some moment but that's it.

I have tried bios and driver stuff already but the problem has not gone. With an external monitor I only succeded, if I use "the expand dispolay on other screen" option , but not real dual view.

Do you think
a) the display is not working properly
b) connection display laptop is not working properly
c) video card is not working properly

How much costs do I have to pay to get this fixed??

Thanks for your advise,
Florian