I have two Nvidia cards (an onboard and an added one), and a monitor connected to each one. Monitors are "on", at least the LEDs indicates that they are. But only the one connected to the onboard card ...
I just installed a new graphic card on my computer, and connected a monitor to it. I followed this post http://crunchbanglinux.org/forums/topic/11900/how-to-nvidia-drivers-in-or-debian-stable/ to ...