if this doesn't work edit /etc/inittab. You'll find a line like this:
Code:
# Default runlevel. (Do not set to 0 or 6)
id:5:initdefault:
change 5 to 3 and the next time you boot, you'll boot in a text mode.
(in slackware the X11 mode is 4, but i'm pretty sure in mandrake it's 5 like redhat)