Thx, ndb!

Problem with account password is solved (logged on as root and made password for 'knoppix') but when I type my password and try to log in, kdm starts again.
And this kdm makes me to type that dumb password again, and again....

also tried to boot with xdm, and even gdm (used apt-get to install gnome environment in console, thought maybe problem is in my new KDE) but no luck.
(same thing happens in gdm, and xdm shows kde startup splash screen but no more than that.)

Any solutions?
Again, thanks ndb!