Having problem with Nvidia Drivers

So I am currently using 12.04 and have a GTX 580M, when I go to check the drivers it says that I dont have any proprietary drivers currently installed, so I am unable to download any newer ones (obviously.)
My problem is that I have been told that I will need to install the newest drivers in order for playonlinux etc. When I try and install the .run file direct from the Nvidia site it says that I need to close X Server first, however when I go into X Server it says
"You do not appear to be using the NVIDIA X driver. Please edit your X configuration file (just run nvidia-xconfig as root), and restart the X server."
I have tried this in terminal and get this message
"Using X configuration file: "/etc/X11/xorg.conf".
VALIDATION ERROR: Data incomplete in file /etc/X11/xorg.conf. Device section "Default Device" must have a Driver line.
Backed up file '/etc/X11/xorg.conf' as '/etc/X11/xorg.conf.nvidia-xconfig-original' Backed up file '/etc/X11/xorg.conf' as '/etc/X11/xorg.conf.backup' New X configuration file written to '/etc/X11/xorg.conf'
Does anyone know how I can go about getting this to work?
EDIT: I have tried stopping X Server through terminal and all this does is close the GUI, it still wont allow me to apply the drivers