1) Use knoppix-installer
2) Configure an installation then Quit.
3) Say 'yes' to save your configuration.
4) Edit the file .knofig
5) Look for this line:
# Default value is: yes
BOOT_DISK="yes"

6) Change 'yes' to 'no'
7) Save the file
knoppix-installer
9) DO NOT load a previously saved config as it will find .knofig automatically.

HTH