you may open a console and type
to get a root login.
Also, when you are in graphical mode, Alt+CTR+Fx where x=1,2,3,4,5,6 are login consoles, in most distros
You get back to graphical with Alt+F7 or Alt+Ctrl+f7 (in most distros)
If you want to boot in text mode change as root in the file /etc/inittab the bold number in a line you'll find:
# These are the default runlevels in Slackware:
# 0 = halt
# 1 = single user mode
# 2 = unused (but configured the same as runlevel 3)
# 3 = multiuser mode (default Slackware runlevel)
# 4 = X11 with KDM/GDM/XDM (session managers)
# 5 = unused (but configured the same as runlevel 3)
# 6 = reboot
# Default runlevel. (Do not set to 0 or 6)
In most distros 3 is the text mode and 5 the graphical (in slack 4 is the graphical).
You seem like a newbie to me and I thought I could provide you some extra info to start with.
Hope it helps