[V.IMPORTANT]My screen is turned off

Dear all
i have just updated my OS from Win7 x64 to Win8 x64
but now i don't have any thing on my Laptop screen i have attached an external screen and i see through it but my laptop screen is turned off and i don't know what to do??
i have installed my screen driver but also it is turned off, please help me as soon as possible
my laptop is DELL 5110 with intel HD WDDM 1.2
thanks

Use this driver:

http://www.eightforums.com/graphic-cards/2519-intel-hd-graphics-2000-3000-a.html#post30075

And see this:

http://www.eightforums.com/graphic-cards/2519-intel-hd-graphics-2000-3000-a-13.html#post70232