look at this:
http://linux-sxs.org/remotexkdm.html

[edit]

first if you are running from cd you'll have to start your knoppix X-application server in runlevel 2 using: knoppix 2 then you'll have to set password(s) for your user(s) then you'll have to edit two files, Xaccess and kdmrc both files are in the /etc/kde3/kdm directory.

First thing is to copy the files into /ramdisk then remove the links in /etc/kde3/kdm.

Then for Xaccess you'll need to edit it so the line below is uncommented like this:
(snip)...
* #any host can get a login window
(snip)...

for kderc you'll need to edit the line below [xdmrc] so it is changed from false to true like this:
(snip)...
[Xdmcp]
Enable=true
(snip)...

then you'll need to link the newly edited files to their proper places like this:
ln -s /ramdisk/Xaccess /etc/kde3/kdm/Xaccess
ln -s /ramdisk/kdmrc /etc/kde3/kdm/kdmrc
then one last step, starting kdm:
/etc/init.d/kdm start

then login and enjoy, if you are running a hd install you won't need to worry about copying and linking the files, and once you get the files edited and running you can make your system startup using kdm by making a link in /etc/rc5.d to kdm like this:

ln -s /etc/init.d/kdm /etc/rc5.d/S99kdm

[/edit]

HTH

rock