Q: Is this a failed GPU? 2007 MBP white screen over readable desktop 8600m gt

The built in 15" LCD is distorted, looks like white wash over the screen, can still see the desktop and windows and menu bar but there is distortion, like some pixels didn't draw correctly.

And weirder, when I plug a 23" LCD into the DVI port on the side, the image is perfect.

Is there 2 GPU's? How could the 15" be distorted and the 23" not?

Thanks for any help and suggestions