Are you still having problems? I have a Dell Latitude something (it's brand new) and hooked up a second monitor without problems yesterday...although people have already gone into it, here were my steps:
Hooked up the second display (analog 15" LCD)
Booted the machine. While booting, the second screen showed a mirror image of the primary screen.
When I got into Windows, the second screen was blank. Went to display properties, and there were two screens shown (1 and 2).
I clicked on the graphic of monitor 2. There is a check box called "Extend my Windows desktop onto this monitor". I checked that, and hit apply. The second screen came on and was usable. I then had to adjust resolution, refresh, etc.
I never once had to go into the nVidia application to use the second monitor. If you are still having problems then maybe there is something wrong with the hardware, because it should just work (I know, I hate when people tell me that). Good luck!