Inspiron 9300 dead lcd?

I got a the before mentioned laptop from someone at work who said it had died.  The LCD you can see come on, and the images on it, but it acts like there is no light being put out.  I had another of these laptops that had a failed video card and swapped the LCD screens.  Yet it's still doing it.  I know this LCD is good but am at a loss as to what else could have failed?  I can hook it up to an external screen and it shows everything with out issue.  Anyone have any ideas?