Thanks for the replies.
Yes, I've done mkdir, and with and without explicit -t ext2.
Why so many distros & discs/partitions? "...let a thousand flowers bloom...". One of the joys of GNU/Linux is choice, to see which I like best for whatever application.
For various reasons I have W-98, W-NT and DOS on the PC as well (flame-bait, any-one?!) and keeping my 'older' discs gives more flexibility for their installation constraints, and places to put /boot partitions below the 1024 cylinder limits, etc.
I had only wondered whether knoppix has been 'customised' in some way, so that unlike all other distros I've found it does not 'see' hdc.
JohnnyH