Do the following:-

Download driver from nvidia website (should be the one with A32).
Restart knoppix in console mode (run level 3)
Make sure the downloaded nvidia is runnable (chmod 777 if not sure)
Run the script. You may be asked about gcc. Take the risk and let it run. You may also be asked anout re-compiling the kernel. Re-compile it.
Modify /etc/X11/XF86Config-4 by changing the "nv" driver to "nvidia".
I suggest you reboot back to console first.
Try startx and see the error.
If it does not work, it is most likely to be due to depth and resolution setting. Experiment until it works. Here is a funny thing. The resolution you see here may not be the one you see when you start your computer at run level 5. Anyway, if you see something, change back to run level 5 and reboot.

You should see the nvidia screen and boot into graphics mode.