Laptop Problem...

[md911]

I have an Acer Aspire lap top for almost 6 months now, and just last night i came home to a dark and dull screen, no usually the screen adjusts darker ever so slightly when i take out the plug in cord. But usually when i plug the lap top in the screen goes super bright. Now it is showing that it is plugged in and not running off batteries. As well i fiddled around with the display settings, and its not the colour, contrast or gama that im looking for, its just like the screen has gone dull, and no matter what i do it wont go back to the way it was.....Help!!!