1) In the 'device' section, add the two following lines, edited appropriately for YOUR make of card:
VendorName "nVidia Corp."
BoardName "NV44-A2 nVidia GeForce 7100GS TurboCache"
2) Look up the technical specs of your monitor in the manual or on Google, and make sure that the Horizontal and Vertical rates are correct. If not, change them as necessary. Once the correct ranges are specified, and the X server has chosen a display resolution, the monitor will decide on its own what vertical refresh rate to use. Much of the time, laptop flat panels only use a very narrow range of 50-60 Hz. Infact, it can be dangerous to your hardware to run such flat screens on laptops at excessively high rates, and can damage the display.
3) The nVidia driver, when installed, removes any previously existing driver. It can only have ONE of itself installed. Therefore, if it is working and shows you the logo on startup, you can be fairly certain that it IS the driver you installed. If in doubt, type 'lshw' in a root console, or look in your system menu for a 'Info-Center' area, and verify the driver release version there.
4) There are no MODES section in your Screen section. In the Subsection "Display"
area, there should be a line like:
Modes "1600x1200" "1280x1024" "1024x768"
but change the resolutions to which one(s) you want available for your system.
Does this help?