A Knoppix HDD install will contain the same settings as you booted with. So the *easy* way would be be to do a reinstall. You could also check the bootscripts used by knoppix (they are in /KNOPPIX on the CD?) and see if you can decipher what lang=it does and add that to your startup scripts (don't ask me where...)
I'll give that a go next weekend. Or someone could tell me where it's hardcoded so I can try some judicious editing.

You really make my point for me with the paper sizes and such: in the UK we've not used (and it's been just about impossible to buy) letter for 30 years or so, and it's actually illegal to sell stuff by imperial weights (although legal to sell by metric and imperial). Oz and NZ use metric. Only US and Canada still use "letter". Drives me nuts with US dictionaries, badly translated German(!) page descriptions (what's wrong with "odd" and "even" FCS?) and so on.