# 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)
The above is from the file /etc/inittab and sets which runlevel the OS boots into (in my case Slackware, and the graphical run-level is init 4) as you can see, the line id:4:initdefault:
sets it to init 4. On your system, check what this line reads in your inittab file.
That should help!
NOTE - you'll need to edit the file as root.
To start X, I would type 'telinit 4
' while logged in as root.