Help with external monitor on my Compaq R3000.

I have found that when I boot up knoppix while my external monitor is plugged in, I doesn't work. My laptop display is fine but the external is all screwy. However if I wait until KDE is completely booted up, then plug in my rosewill widscreen in, it works like a charm. That doesn't bother me, what does bother me is that I want to turn my laptop display OFF while using my external. In fedora core 5 it wasn't a problem I could just keep the external plugged in and when gnome booted up, it would turn off my laptop display. How can I get around this problem?

[EDIT]

One more problem. When I try to play a video in xine, the video plays fine on my laptop display but i get a blue screen on my external monitor. any ideas?