Chime, Logo, Gear, then a white screen.

I have a 17" non-unibody Macbook Pro A1212 whose serial number ends with W0M.

I got it as a repair project. Previous owner wasn't able to erase the hard drive completely. I confirmed her findings:

I hear a chime, see the Apple logo, then the rotating gear icon. Then the screen goes completely black for an instant (probably with a backlight) before going gray/white and there's no further activity (optical or USB drives wind down).

Upon hooking up an external DVI monitor, the gray/white screen shows up on the external monitor and the native LCD shows the Apple logo.

I have replicated this behavior after switching memory and batteries, after using and unplugging the external monitor, after using boot DVD's internally and externally (via USB) and bootable USB drives, and after erasing the native hard drive (in another machine). I have also reset PRAM and the SMC.

The native hard drive (100GB) passed Disk Utility's Verify Disk and HD Tune's Quick Test on the PC Side. I have yet to hear clicks of death.

The only instance that progressed past a gray/white screen featured a mouse pointer against a gray/white background.

I tried booting from Hiren's Boot CD and got a backlight dark screen when I was expecting the top-level text menu.

I'm thinking the nVidia chip has gone bad, but I'd love some other thoughts.