xorg.conf is usually located in /etc/X11/
I have an inspiron 8600 which was a "mother" to configure....
First things first....after your install, did you do an X -configure at the root prompt?
If no, then open up a console (as root) and type X -configure (or X -Configure) -- one of those....this will make a xf86config file based on what is detected in your pc....audio/video...etc. I use slackware, so it might be a bit different. Once complete, should store this file in your /root directory. Use your favorite editor (i.e. pico or vi or whatever) to view the files....this should get you started.
Next, go to the nvidia website and download the latest drivers for linux. You can find them at http://www.nvidia.com/object/linux_d..._1.0-6629.html
The page has a step by step instruction, so you should be able to install pretty easily.
Try those things and let me know how it goes.