Since around Fedora 8 and KDE 4.0, the default DESKTOPMANAGER that greets you before you login to your GUI  is  set to GNOME (Even now with Fedora 13 out, the same is still true).  Now I was an avid KDE user and though I started on Gnome, KDE just grew on me up until about Fedora 12.  After that, I'm now a GNOME user, pending numerous fixes the KDE team is still working on.  The fact that I had a GNOME login panel at the beginning as I'm going to login to KDE didn't really make at the time.  Now I have another reason.  What I wanted was something that looked a little bit more completed:

 

Here's how to enable switching your default login promt from GNOME (GDM) to KDE (KDM):

Enabling the root account in KDM Display Manager (If it doesn't exist, create this file with KDE or XDM as the selection):

[root@lhs Documents]# cat /etc/sysconfig/desktop|grep -v \#
DESKTOP=KDE
DISPLAYMANAGER=KDE
[root@lhs Documents]#

The above file is loaded and looked for by:

/etc/X11/prefdm

which has the following definition logic for loading the settings:

if [ -f /etc/sysconfig/desktop ]; then
        . /etc/sysconfig/desktop
        echo "prefdm: Using display manager '$DISPLAYMANAGER' from /etc/sysconfig/desktop ….";
        if [ “$DISPLAYMANAGER” = GNOME ]; then
                preferred=/usr/sbin/gdm
                quit_arg="–retain-splash"
        elif [ “$DISPLAYMANAGER” = KDE ]; then
                preferred=/usr/bin/kdm
        elif [ “$DISPLAYMANAGER” = WDM ]; then
                preferred=/usr/bin/wdm
        elif [ “$DISPLAYMANAGER” = XDM ]; then
                preferred=/usr/bin/xdm
        elif [ -n “$DISPLAYMANAGER” ]; then
                preferred=$DISPLAYMANAGER
        else
                quit_arg="–retain-splash"
        fi
else
        quit_arg="–retain-splash"
fi

If you will be using the root account (generally frowned upon in Linux circles) uncomment the first occurrence of this entry:

[root@lhs Documents]# cat /etc/kde/kdm/kdmrc|grep AllowRootLogin
AllowRootLogin=true
#AllowRootLogin=true
[root@lhs Documents]#

Alternately, one can change the login prompt using a GUI option:

[root@lhs log]# kcmshell4 kdm — GUI Editor for the KDE login prompt screen.
  /usr/bin/switchdesk  — switch desktops.  Looks like Gnome to me!!!

Possibly the default login now works sicne I have this file (?):

[root@lhs ~]# cat .dmrc

[Desktop]
Session=kde
Language=C
[root@lhs ~]# pwd
/root
[root@lhs ~]#
 

apparently, the choice of whether you use the KDE or GNOME session manager also impacts if your .Xauthority file will be generated or not.  You can also check out these folders for the other session managers:

[root@htpc ~]# locate Xsession
/etc/X11/xdm/Xsession
/etc/X11/xinit/Xsession
/etc/gdm/Xsession
/etc/kde/kdm/Xsession
[root@htpc ~]#

Cheers!
TK