It sounds as if your backlit display is defective. You can attempt to purchase a replacement display and install your self or you can have someone (there are many notebook repair shops around the globe).
To verify, simply connect your notebook to an external monitor to ensure the system is still functioning normally otherwise.
thanks a lot man!!
i ll check out with an external monitor
but is there any chance of smething going wrong with nvidia or motherboard??
because i just want to have an estimate of the repair!! (i just pray there is no chance of sme problem wid d nvidia!!