I selected 1280x1024, 1024x768, 800x600, and 640x480 as my possible screen resolutions during install. I have edited /etc/X11/xorg.conf because my monitor was not recognised. This file shows the required resolutions under "Screen". I have installed Nvidia drivers.

When I use System>>Preferences>>Screen Resolution, I find that I have far more resolutions to choose from, and what is worse, they do not work properly, making it very difficult to change back.

Could anyone tell me how to remove these useless options from the menu.

hmm, my xorg.conf doesn't have all those resolutions listed

however they are available in System>>Preferences>>screen resolution

just like you describe...

i've never worried about it before.

do you change screen resolution often?
if not, then just set it and leave it

I should have said that this is rather important to me. I am developing something that will be used by other people in separate organizations. As this fault allows them to wreck their system, I need to fix it.

i bet there is a gnome preference somewhere that you can limit those options.
i did some searching but couldn't come up with the answer.

seems like there should be a way in gconf-editor

you might try posting in a gnome forum

I did a search for one of the odd screen resolutions (928x696) and found it in: /var/log/Xorg.0.log

There are a huge number of resolutions listed there but I have no idea how only some are selected for listing in Gnome. As the string "928x696" does not occur elsewhere, I conclude Gnome must get the string from the log file unless it generates it from some other information.

The log file claims the list of screen resolutions comes from a config file and lists /etc/X11/xorg.conf as its config file (it certainly gets some of its information from it); but no way does it get all those resolutions from that file (only the ones actually required are included in it).

gconf-editor only lists the default resolution: 1280x1024 @ 85Hz.