When you first boot up the FC4 CD (and you're at the options screen), there should be a button to press eg: "Press F2 for help". If you go there, there should be an option for changing the screen resolution.
If not, you can add the following phrase to the boot parameters: "xmodule=vesa" (without the quotation marks). That should give you a decent resolution.
Ps. Welcome to LQ!