thank you for your advise..
i did not make a backup for my /etc/X11/xorg.conf
after update the xorg.conf the file seem to be crashed.
so i try to install the slackware again
and i choose ps/2 for my mouse and disable the gpm program.
then startx can load normally and succesfull.
why i choose ps/2 and disable the gpm program because from the xorg.conf in previous installation said that "cannot open core device" something like that
so i think that i should try to use common setting like ps/2 and disable gpm program so that it would not start at boot.
it is correct?
and if in the future i had the same problem what is the action should i take to resolve it.