problem on installing nvidia driver on my lenovo z570

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http://askubuntu.com – i have lenovo z570 , nearly i found that my laptop has two Graphic Card (intel + nvidia) !!!!! when i want to install nvidia driver , i've got an error witch is said " the graphics driver could not find compatible graphics hardware " what should do to fix it !? my laptop realy doesn't have that hardware ? (HowTos)