Problems Changing to 19" Monitor

OS: Suse 9.0 and 9.1 Monitor: IBM 7574 Both were originally installed with smaller monitors. This is an IBM Industrial Graphics Monitor and is not listed in the YaST list of monitors. I've tried everything I can think of to define it so the GUI (KDE) sreen uses all of the screen area; currently it looks like a 17" dipaly area with rather large black borders. Character screens use all of it just fine. What am I missing here? How can I restart the GUI (so changes take effect) without rebooting the system? Thank you, Lucky Leavell