For a newbie, the best way to install the latest version of knoppix is to download the CD and install it the same way you did the first time. apt-get dist-upgrades are highly dangerous and will likely turn on a bunch of daemons by default that you have no use for. Knoppix is very optimized out of the box, but running a dist-upgrade on it will kind of mess up that divine balance. Best suggestion: back up your data and home directory, and install the latest version over the old one. This will bring you up to a very current version of KDE btw.