Here goes. I know you guys have gotten a bunch of questions on this exact subject, but the threads either end up not completing or there are terms thrown around that I can't begin to recognize. So, that said:

I've got a Dell XPS with a 19" (Dell) E196FP monitor (flat panel). Op. resolution is 1280 x 1024 with a 60 Hz refresh rate. My video card is an Nvidia GeForce 6800. I'm running Windows XP. I've got a boot CD for Ubuntu 8.10, and after the problem occurred the first time I went and burned one for Fedora 10, to the same effect. This is about the extent of my knowledge and experience with anything, so please bear with me. I'm here to learn.

Here's the problem. Both systems show a startup screen, then the screen goes black and displays "Cannot Display This Video Mode. Optimum Resolution 1280X1024 60Hz." Contrary to what I've seen in some other posts, it does not float around like it's a screen saver. (I don't think this is of any significance, but I'm giving everything up because the devil is in the details, as they say.) I know that this is a monitor problem, and it seems to be common to flat panels. So I tried to access my monitor menu, but no success. I've been in Control Panel and I've adjusted the resolution, but I think it defaults to a different resolution when it boots.

Sorry for the length of the post, but I hope that what I've written will help. If you try to help with a solution or ask for more info, imagine you're talking to a child who has never used a computer before. That should get the best answers out of me. Thanks in advance.

Cheers,
Alan

Post relevant part of /var/log/Xorg.log

Use ksystemlog for that

driver nv or nvidia or nouveau?

I have a Dell XPS Gen 5 with a 1905FP monitor. I always have graphics with a new Linux installation, but not optimum res. also. The reason is:
The generic drivers Linux has only gives minimum graphics, just like Windows, if you want better you'll have to install proprietary drivers from Nvidia. Because your Dell Computer came with all the necessary drivers bundled in the CD or CDs, it is usually not a problem when installing the OS. But the Linux you downloaded does not come with proprietary drivers specific to your hardware, mostly because of license issues and the fact that it was not supplied by Dell for your specific hardware.
Go to Nvidia's web site and download the latest Linux drivers for your card. If you are using Ubuntu, you'll need to install "build-essentials" through the package manager, then from the directory your Nvidia script is in issue command: sudo sh NVIDIA-Linux-whatever-version.run to build the driver. When asked if you want it to configure the xorg.conf file say yes.
With Fedora you need to install kernel-devel package with package manager before running the sh NVIDIA-XXXXXX.run command.

So how can I do any of this without actually getting into Fedora? (We're gonna go with Fedora, for the sake of argument.) Sounds to me like this is stuff that can only be done within Linux, but I can't even get into the OS at all.

Driver is nvidia. Other than that, I don't understand any of what you said.