ctrl-alt F1 (or f2-f6) should get you to a command prompt
" shutdown -h now " will shutdown linux so you can turn your computer off.
I'm a little curious as to what kind of video card you have, etc. I had a similiar
problem with the GUI the first time I installed debian not so long ago on a rather old
celeron machine. I went through a little bit of trouble getting the i810 drivers installed
correctly. When using xf86config if I chose i810 nothing at all would happen due to
agpgart not being loaded. When I went through the list of other drivers using
xf86config to see if something else would work I recall vesa and the generic vga drivers
would actually load the gui, but the top two inches or so of the screen was replaced
by crap and the time would pop up wherever the mouse pointer happened to be
at the immediate moment. After about a minute I'd have a horrendous looking screen
full of little clocks.
Anyhow, if your screen is screwed up that badly chances are it's not configed
correctly and isn't something that can be fixed within kde.
Out of more curiosity, what version of the linux kernel does slackware 9.1 use?