The Screen remains blank, why?

Good question.

For this particular model, the back light is integrated into the LCD panel. The issue lies at one of three points: 1) the LCD panel itself has gone bad, 2) the cable connecting the LCD to the system board has gone bad or become loose, or 3) the system board has stopped sending video to the LCD connection. Just because video is available through a VGA port doesn't mean that the system board is perfect.

I would start with the simplest solution, which is to check the cable itself. Even if the connections are solid, you might want to unplug and re-plug them.

I don't recall exactly where the LCD cable is within the base, but I believe it plugs in by the fan and can be adjusted without fully disassembling the unit. At the other end, there are two screws at the bottom of the LCD bezel which need to be removed. The bezel will then snap off (be careful not to break it) - revealing four screws that hold the LCD down against the cable.

Good luck!