Hi snow:

I don't know where is the problem. As says Cuddles if you did a hard disk install (knx-hdinstall or knoppix-installer) you where requested to enter a root password and other one for the knoppix user. Ok it is at least if you do a debian install. If you did a knoppix install (the same as Cd) the password is truncated and you don't have to enter it, and you weren't ask for it.

So, did you do a knoppix-like installation?

if you do, the only way I know to run programs as root is typing the
commands in konsole. Your login would be always as a simple user. I
recommend you reinstalling it in debian-like mode (or through
knx-hdinstall)

If you did a debian-like installation the problem would be that you have selected autologin when starting the system.