Salve Andy,

>I'm planning to try out a HD install on my laptop which has a 20G
>drive.
If you install Knoppix additional to your running system, you
need seperate partition with > 2,6 GB(AFAIK) free space.

>I've read that when you upgrade to a newer version of Knoppix it >wipes out the old install.
[..]
> Should I create another partition for /etc? Whould this get wiped
> by an upgrade?

See Knoppix as a clone of an installation. There will be no upgrades
with Knoppix, only new installations. Knoppix is a Live-System and
not a distribution.
After installing Knoppix to your hd, you have a Debian installation
on your hd. You can use the Debian tools apt-get to install and
upgrade your system and software.
visit http://www.debian.org and learn more about Debian.

If you use a seperate /etc before installing Knoppix again,
you use an old-fasiond installation in /etc. This will not run,
create trouble or unnessesary work. So again, after installing Knoppix
on your hd you have two options:

1. To install a new (instant - clone system) Knoppix over the old one
2. To use the debian tools.

BTW, i see no reason why to split your hd in so many partitions,
it is more complicated, less flexible and not faster.

Special Partition for /boot swap are home are handy:
>I then usually have my data area on another partition which I mount >as /home/myusername

Visit
http://www.linux.org/docs/index.html
for general Linux knowledge.

Greetings
rob