I tried these on the commandline, and remembered to do "su" first:

knoppix@Microknoppix:~$ su
root@Microknoppix:/home/knoppix# aptitude install flashplugin-nonfree
E: The value 'wheezy' is invalid for APT::Default-Release as such a release is not available in the sources
E: The value 'wheezy' is invalid for APT::Default-Release as such a release is not available in the sources
root@Microknoppix:/home/knoppix# aptitude install flashplayer-nonfree
E: The value 'wheezy' is invalid for APT::Default-Release as such a release is not available in the sources
E: The value 'wheezy' is invalid for APT::Default-Release as such a release is not available in the sources
root@Microknoppix:/home/knoppix#

Any idea how can I install flash player, then ?

The Knoppix version is this:

KNOPPIX_V7.0.3CD-2012-06-25-EN.iso28-Jun-2012 11:27 693M


http://lame.lut.fi/linux/Knoppix/KNO...2-06-25-EN.iso