Being root do the following:
To make sure you have a backup of the original file:
cp /etc/inittab /etc/inittab.org
If any of the below does not work and render your /etc/inittab useless you can always replace it by the original by doing cp /etc/inittab.org /etc/inittab
Goto the line that reads id:3:initdefault:
using your arrow keys and put your cursor on the 3.
You should have exited vi and returned to the commandline.
To check if the line was indeed changed: grep initdefault /etc/inittab
The line shown should show a 4 instead of a 3.
After the next reboot you should end up in a GUI environment.
For X related info:
There are different runlevels (RL) and what they are used for:
# 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
In simple, human readable terms: 3 will give you commandline mode and 4 a gui.
Is it somthing i did wrong during installation?
RL 3 is the default runlevel for Slackware (and should be for other linux/unix distro's).
More and more disrtro's (RH, Suse, knoppix etc) start in gui mode, which is RL 5 (or 4 in Slackware's case). Officialy 5 is for GUI mode and 4 is free/reserved.
Hope this clears things up a bit.