Since your Intel processor integrates a graphical chipset that the (libre)
kernel well supports, the best would be to physically remove the nVidia card
and use the Intel integrated graphics. You would not only gain performances
but also save energy.
If you don't, "nouveau" should be running. There is no need to install
anything or to edit /etc/X11/xorg.conf. So if I were you, I would (re)move
that configuration file:
$ sudo mv /etc/X11/xorg.conf /etc/X11/xorg.conf.bak
Then reboot (you actually only need to restart the X server but well) and
show us /var/log/Xorg.0.log (attaching it to your post) so that we can check
whether "nouveau" really is handling the graphics. To improve the support,
install a more recent kernel (that will include more recent drivers)
following the instructions on http://jxself.org/linux-libre/
