I have two hard-drives, one with Linux Fedora Core 4 and the other with Windows XP. There are no monitor errors under XP, but when I boot up Linux I recieve the error: "Not Optimum Resolution: Recommended Mode 1280 X 1024 60Hz"

This error is reported over the Linux login box, by a monitor specific window - not by a Linux error. The box will fade after several seconds allowing me to login. When the login completes the screen goes black and the error box appears again, this time bouncing around the screen as if to taunt me!

I am unable to get to the fail safe login, and I have tried changing monitor settings under XP and then trying them again in Linux - still the same error.

Using a Radeon 9600 XT Pro with a Samsung 17' Flatscreen, could the error possibly be a driver in Linux? If so, how can I fix that if I am unable to login?

The box that appears is from the monitor itself-- not related to the video card or drivers. It probably means that you/Linux are trying to use too high a resolution or too high a refresh rate. Changing settings in Windows will not help. I would change the xorg.conf file to use 1280 x 1024 @ 60Hz from the command line- type ctrl-alt-backspace to get out of the black screen to a console.

How do I edit the xorg.conf file from the command line?

First, you need a console. Press ctrl-alt-backspace to get one. One way to proceed is to type "xorgconfig" and press enter, and follow the prompts. There are several guides on how to do this online, and it doesn't matter what distribution they are meant for. You could also do it manually, but this is harder, and based on the fact that the monitor was set wrong, there may be other errors. I would advise using xorgconfig.