If the monitor is connected via VGA, you should try to connect rather via DVI.
Otherwise, you can try and use PowerStrip.
See this tutorial how to Customize monitor resolution settings with PowerStrip, which says:
Two primary software components, the
video driver and the monitor driver,
affect the quality, resolution, and
color depth of the image on your
screen. As I mentioned, PowerStrip
doesn’t replace your video driver; it
supplements it. So Windows still uses
the original video driver. One of the
ways that you can use PowerStrip to
supplement the video driver is to
create custom resolutions.
See also this Powerstrip guide from which I quote:
Powerstrip is very powerful, but also
quite capable of causing your computer
and display to stop "communicating"
properly, this could cause the display
to start rolling, doubling or
generally freaking out. It is
important that you don't freak out as
well. It is recommended that you know
how to start up your computer in
"Safe" mode and "VGA" mode, uninstall
and reinstall drivers and get around
in "Device Manager" if you wish to use
I would also recommend having backups to your data and creating a system restore point, before installing and using it.