Have you installed X?
I take it by mini CD you mean the netinstall CD. If that is the case, then you don't have X yet and must apt-get it. You could try a apt-get install KDE and that will do it for you (might also want either KDM or GDM or XDM). Note: I'm not too sure about the command for KDE---I'm a flux guy, so I just do apt-get install fluxbox.