Help with multiple monitor support

I am trying to use Knoppix 4.0 on a couple of different laptops. One of them, a Dell (ironically), works flawlessly. The other, a Pentium 4 1.7 GHz with a Radeon 7500...not so much. My problem stems from the fact that I have to use the external monitor port. This laptop was damaged about three years ago when someone tripped and fell on the case hard enouch to cause impact damage on the screen, which gives me a nice black design spidered across my screen.

I just discovered that my problem isn't as bad as I thought, but I'd still like to see if there's a way around it.

If I boot the computer with an external monitor attached, KDE boots with the external monitor set to something that looks horrifically like 320x240, and the laptop LCD at 1024x768. If I try to open anything, including the control center and the shut-down control, the screen starts flickering uncontrollably. As I just discovered, everything works beautifully if I just wait until after KDE is through loading to plug in the external monitor. I don't mind doing this, as it's just a matter of when the secondary monitor is plugged in, but is there any cheat code I can use to get around this? I like to leave the monitor hooked up. Like I said, it's not a big deal if I can't, I'm just looking for resolutions.

UPDATE: Just realized I forgot to mention the brand of laptop. It is a Winbook J4.