A good place to have a look about this would be
here.
It's been a while since I had a go with knoppix hard disc installs.
Presuming that yourself as a user say NoviceW, with a password etc, it could be a permissions thing if you didn't add yourself to the various groups. Don't forget, when running knoppix from the cd, you are by default logged in as user knoppix so,
Have you tried logging in with knoppix as the user name, with knoppix as the password? because if you can do that then you should be able to then do
and change the root password for your install.
That's from memory, I may easily be wrong.
Once you're in as root, then start doing the changes and modifications to enable you to play with the system properly i.e. make sure you know which groups user knoppix is in, make yourself the same, then you can always make user knoppix hidden in the kde login manager, or delete it completely.
hope this helps
regards
John