if startx doesn't work,
install the graphics drivers, (if you have an NVidia or ATi)
do an xf86config or edit /etc/X11/XF86COnfig manually
if startx does work, edit your /etc/inittab and tell it the default run level is ... what 4 or 5 ?? (in slackware it's 4, in every other distro i've seen it's been 5, but there are comments in the file that explain it either way.