A poor mans install is a copy os the compressed file on the hard disk, still in compressed form. Your use that just as you do the CD. the upside is that a hard disk is faster than a cd, the downside is that you still have a compressed file that can't be added to or changed.

Other Knoppix installs try to put the uncompressed files on the hard disk. They require more space, but in theory you should be able to install other software, update packages and do other Linux like things. Unfortunately, because of a design choice of Knoppix, this theory usually fails and non-poor man installs often have problems, either immidately (networking often fails for example) or after installig new software or updating software.

If your notebook runs the CD then you should be easily able to install Debian or some other Linux distro intended for hard disk on it. This would allow you to install only the software you use (potentially saving a lot of disk space from stuff Knoppix drags along that you don't care about) and install other software safely. That is my suggested approach.