Knoppix has three ways to do an HD install.
One;= just place the knoppix img on any drive partion currently occupied by another install, and place the boot folder contents in the boot folder, and edit grub. This will give you a live CD session running from the HD, it's unchange able unless you have the tools and know how to edit an img file.
This install is not at all like sid, it's an exact copy of the live cd.
Two;= You can do a debian type install to the HD, But you have to do some configuration because you lose all the hardware detection, and it unlocks the root account so you normal user won't have all the power it had in a Live CD session. I personally didn't like this method.
This one is a very convoluted version of debian full of knoppix junk. In my oppion very undesirable.
Three;= You can do a Knoppix type HD install, this basicly does a debian install to the HD but keeps all the functions of the live CD, root account is still locked, your normal user is knoppix and has sudo functions, the HD detection still functions etc. Except now you can apt-get and uninstall or install more software.
This is a high breed debian install, more like ubuntu than debian to be quite frank.
If your interested in Sid, I come accross a distro last week called "sidux", I've found it to be quite pleasent. And have installed it on my of my boxes so far I've not had any problems. You can download ethier a CD or DVD each of which are live sessions like knoppix but will do a HD install and give you a native debian system.
Quoted from thier wed site. http://manual.sidux.com/en/welcome-en.htm
sidux is based on Debian 'sid' GNU/Linux, and holds fast to the core values and social contract of Debian.
You no longer need to wait for a new release to always have the latest of anything, including kernels. Once you have installed sidux, all it needs is a dist-upgrade, which is a system-wide software update from debian and sidux.
This means that re-installing yet another release every 6-12 months on your PC is unnecessary with sidux, as the weekly or monthly dist-upgrade brings everything up-to-date, except the kernel; which may be upgraded separately as required.
As it is, an install with sidux usually does not take longer than 20 minutes.
sidux offers 4 up-to-date live-CD//DVD entry point release variations, these are:
* 32 bit lite, live-cd approximately 550MB +/-
* 32 bit full, live-dvd approximately 1.5GB +/-
* 64 bit lite, live-cd approximately 550MB +/-
* 64 bit full, live-dvd approximately 1.5GB +/-
With the 'way of sidux', you will be always up to date and have the very best that sidux together with Debian 'sid' can offer.
I've been quite happy with this distro. But still use Linux Mint on my laptop.