that's really weird.. mine has been working out of the box since Slackware 13.0. you shouldn't need to install anything else. I use kernel-huge, try booting that one first and then check if the module is loaded.
first remove the driver you installed to prevent conflicts. then, edit /etc/lilo.conf and point the booting to your kernel-huge in /boot . If you did a full installation, it should be there. I don't use lilo myself but it should look similar to this
# Linux bootable partition config begins
image = /boot/vmlinuz-huge-kernel-version
root = /dev/sda6
label = Slackware
# Linux bootable partition config ends
don't forget to run
to update the configuration.
after booting, check if the module is loaded.
(the name of the module is iwl3945 under iwl_legacy)
otherwise, load the module.
if you use GUI, try using wicd (can be found in slackware official repository under /extra) or NetworkManager (should be installed) to test the wireless. start NetworkManager first
#chmod +x /etc/rc.d/rc.networkmanager
then it should be loaded automatically in KDE and XFCE when either one starts.