Ubuntu :: Switch Monitors With Terminal Or Keyboard?

My laptop screen broke (smashed) a while ago and I have been using Windows with an external monitor on it ever since. My main laptop, however, runs Ubuntu 10.04 which I prefer immensely so I installed it on my broken laptop in dual-boot with Windows. Everything was fine at first, it loaded by default into a dual-monitor mode, but that was easily changed to just the single external display.

The problem was when I installed the graphics card driver (a Nvidia one). It seemed to reset the configuration to just using the laptop's broken built-in monitor. From what I can tell, there is nothing wrong with the driver as the OS seems to be running fine (from the small corner of the screen which still works). Unfortunately, neither the FN-F4 key combination (which never worked on Windows either) nor unplugging/reinserting the HDMI cable resets the screen setting to let me use the attached monitor.

So my question is whether there is anything I can do using the full-screen terminal (CTRL-ALT-F1), or a keyboard shortcut, to change monitor or go to dual-monitor mode. I would prefer not to use it to just disable the graphics driver because the laptop is a Samsung r780 and the only reason I really want to use it is its great graphics card which is way better for editing stuff and 3d tasks than the old replacement I'm using at the moment.