My friends Dell Laptop that he recently bought monitor gone really dark... you can still see some of the displays but it is very dark. He did not play with any brightness or any other settings. He just says he turned it on once and it was like that. I had it plugged in to my monitor and on my screen everything is fine.
Its still on warranty so easiest thing is to call them up and get them to fix the pile of trash but I was hopinging there might be a way to fix it myself.
More aboutdell inpiron 1545 monitor failure
It could de the back light has gone bad or the power for the back iight.