Switching from GNOME to KDE
 

Where do I find the option to have Linux use KDE and not GNOME.

in your home directory,
eg. /home/kau/
open a file called .xinitrc. if this file does not exist, create it. please be careful to include the dot in front of the xinitrc file. ie .xinitrc
then edit the file by adding the line below:
startkde
comment any OTHER lines in that file out by placing a # in front of the line.
then start your X session.

In slackware there's a util called xwmconfig, you can use that, or you if you use graphical log in you can switch right there on the log in after you type in your login and password (before you press enter!)