Actually, installing from Knoppix to hard-disk is relatively easy. I use it for my family's main workstation. It takes around 30 minutes to install, and then you've got a Debian system. Knoppix installs with a whole bunch of instant, useful software including OpenOffice, Mozilla, xine, xawtv, KDE, k3b, frozen bubble (my wife's favourite) etc. most of which require no additional configuration (well, xawtv does require some tweaking to change from the default European PAL tv format to North American NTSC). Additional software, such as Mplayer, is just an apt-get away.
You can find Knoppix documentation at http://www.knoppix.net
, which is the best site for Knoppix issues. Here is a how-to for Knoppix hard-drive installation: http://www.freenet.org.nz/misc/knoppix-install.html
Be aware that the knx-hdinstall script has been superceded by a new script, knoppix-installer. Check the hard-disk install forum
at knoppix.net for more information.