We have cautioned new users from installing Knoppix to the HD without first being aware that it might not work for them http://www.knoppix.net/wiki/Hd_Install_HowTo. You have run into a known issue with Knoppix 3.9 HD Installs in that it breaks networking.

The bug is documented as #15 http://www.knoppix.net/wiki/Bugs/3.9-2005-05-27 and can be resolved by entering the command as root user:
ln -s /etc/init.d/ifupdown-clean /etc/rcS.d/S18ifupdown-clean
Then reboot the PC.

Let us know if this is successful.