I have the same problem and have it solved (50%).
My laptop went white when start and there is startup sound and I able to shutdown via keyboard shortcut.
In my case, it's the cable that conect LCD with the Motherboard.
I open up my laptop (the whole shebang), and I ended up with a cable that only need a little push. It loosen from the "place-it-should-be".
Now I got it, but every time I start up my laptop, i have to push the cable.
For the record, i let some of the casing open so I can push the cable.
Here is the picture.
That 2 cable is connecting the LCD panel with the motherboard.
Only with the push, it'll work.
I hope you guys have the same "easy" problem.
For the record, this cable worth Rp 400.000 in USD, it's about $44.
I rather using the push than purchasing a new cable. :D