External Monitor as Primary/Default Display

I recently installed Lucid Lynx on my Dell Inspiron 9400. One niggling annoyance was that the Dell's LCD screen was the primary display, whereas I wanted my external monitor (BenQ T2200D via DVI) to be the primary display.

Ultimately, the solution was simple:

1. run the NVidia X Server Settings tool (gksudo nvidia-settings)
2. in the X Server Display Configuration I made sure the Dell's display (Seiko) was disabled
3. when saving to the X Configuration file, i.e. /etc/X11/xorg.conf, I chose not to merge with existing file
4. restart X
   

Install latest nVidia GeForce drivers

The Dell Inspiron 9400 I have comes with the nVidia GeForce Go 7900 GS graphics card. There are "restricted" (closed source) drivers for this card with superior support for hardware graphics acceleration compared with the default open-source "nv" drivers.

To install the nvidia drivers I used "Method 1" from this excellent guide

1. installed the nvidia-glx and linux-restricted-modules-2.6.15-23-686 packages
2. enabled the driver using sudo nvidia-xconfig
   
3. added the nvidia-settings dialog to the Application > System menu
4. Restarted xserver (Ctrl-Alt-Backspace)
   

It worked flawlessly.