I have two Toshiba laptops and both behave the same way: the problem with the screen is due to the fact that Knoppix does not recognizes the video adapter, and so uses a default one with a resolution of 640 by 480, that Toshiba laptops show in the centre part of the screen.

Two are the solutions. a) there is an option, in the setup of the machine (accessed by a utility program, often in the rescue CD, or in a floppy - depends on the model) that says more or less "enlarge the screen". This is to show full screen the resoution of 640x480. But it shows up very bad!

b) The best solution is to correctly configure the X server. To do this, you have to get at least the manufacturer and the model of your video adapter. Then, when running Knoppix, you have to type in a terminal window (something like tho a DOS prompt window in Windows) the command "kxconfig".

This brings up the X server configuration utility. Now, you can choose your video adapter and set it up. Be sure to set a resolution of at least 800x600: otherwise the problem will not be removed. And, last but not least, at 640x480, even if displayed on full screen, the room on the display area is very small, and most windows does not fit into.

Once finished configuring the display, to get the new settings, you should restart the X server, by hitting CRTL+ALT+BACKSPACE.