Hi, I was having the same problem as you, I'm also pretty new to Linux and Knoppix, but I have managed to rectify it.

I have a 3c2000 on board NIC, but the 3c940 and the 3c2000 share the same driver.
You can download the 3c940 driver from here: http://www.asus.it/support/download/...odelName=P4P8X

Once you have downloaded it you will have to build the driver module. Simply copy the 3c2000.tar.gz to the Knoppix desktop and extract it by right clicking it and then selecting 'extract' from the menu then open the folder it extracts to.
Next click tools then 'open terminal' The command window should open at the current directory where the driver is extracted.

Now type 'make install' and the driver should begin to build.
Once it has finished the driver module will be named 3c2000.o

The next step is to copy the driver module to a floppy disk.
Reboot knoppix with the floppy in the drive then at the boot prompt type 'Expert'
Follow the prompts until it asks if you want to load any other modules from a floppy.
Let it find the module then it will ask which modules you wish to install. Type 3c2000.o and then the driver should load and your card will be detected.
Then just continue with the prompts until knoppix has finished loading. You should now find the driver is loaded and you card is ready to use.

Let me know if you have any problems and if you get it working OK.

P.S. I'm typing this from Knoppix right now.