Here I come again with a solution that works, instead of lame comments that don't solve anything... Like I did here:
http://www.knoppix.net/forum/threads...noppix-6/page2
I'm not going to address using the Knoppix distro as your desktop system, however to disable autologin on Knoppix 6.2, create a boot thumb drive - use the directions supplied in the link above. This will create a writeable portion of the bootable thumb drive filesystem called UNIONFS.
One you have done that simply edit the /etc/inittab file as follows:
Replace lines like this:
1:12345:respawn:/bin/bash -login </dev/tty1 >/dev/tty1 2>&1
With this:
1:12345:respawn:/bin/login </dev/tty1 >/dev/tty1 2>&1
Do this for all four tty entries and add tty5 and tty6 as well
Next change your default run level to 3 by changing id:5:initdefault to id:3:initdefault
Next make sure you set passwords for root and the knoppix user
as root
passwd root
passwd knoppix
Save the file and restart - you will now be booted into a console login screen which prompts for the username and password
Once you have logged in, boot into Xwindow if you so desire as follows
sudo /etc/init.d/knoppix-startx start
Whoo-hoo!