i think you may find your backlight as failed ,had mine replaced about two 
months ago after Pcworld told me it could not be repaired  because the cost 
would be to high tried to sell me a new laptop .i have a repair address if 
are interested.<sail1942@yahoo.com> wrote in message 
news:1137772312.554103.69570@g47g2000cwa.googlegroups.com...
>I suddenly don't have any light on my Toshiba M35X-S149 screen. I can
> see the image and the computer works fine with an external monitor. Do
> recent models have fluorescent backlights like earlier models?
>
> Fred Carpenter
>