There are system-wide settings for X stuff and KDE stuff that are stored in other places, and then user settings that are stored in your home directory. So if root can log into KDE and use the same applications as you used to be able to do as user, then the system-wide settings should still be good.

With IceWM working, I'm wondering if it could be a memory problem. How much RAM is installed, and how big is your swap partition - and did you change its size when you repartitioned?

In a situation where memory is marginal, it's theoretically possible that root could still run KDE because its configuration is pretty minimal - by default Knoppix/KDE doesn't want you to run the GUI as root for security reasons - but the user's configuration could be enough to swamp memory and crash KDE.

At least you know that your display manager is working. That's the program that's responsible for putting up the login window. It does almost nothing else to speak of, just being the piece between X and the window manager (like IceWM) or window-manger-plus-kitchen sink (like KDE).

KDE installations use kdm, Gnome installations use gdm, and there's also xdm. But they're all the same size, so there's no reason to think about the display manager any further.

I'm really guessing here, but I'm still making somewhat ed-ucated guesses!

-- Ed