At the boot: prompt try knoppix screen=800x600 vga=normal xvrefresh=60 or failsafe.

BTW what type of video card do you have?
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To answer my own question you have an ATI. A quick Google search came up with this page which you might find of interest. You could add xmodule=ati to the knoppix line above and try 1024x768 for the screen.
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