log in as root in a terminal and type:
dmesg | more --------scroll thru that and see if it shows an ethernet card
lspci --------that will show all pci devices detected
lsmod -------shows all kernel modules loaded, you need one for the NIC
ifconfig -------with no options it will show network hardware status including MAC address--if the NIC module is loaded and its up it will show all that stuff
modprobe XXXX -------XXXX is a kernel module, modprobe attempts to load a kernel module, what NIC do you have?
I will tell also that with linux, you can go thru 100 different distros and its gonna be the same story, at some point you will have to learn the command line, reinstall/reformat doesnt fix anything, it isnt windows
once your ethernet is detected and working you can setup your network with netconfig
it isnt complicated, but with slackware the easiest and quickest way to get somethings done is the commandline, dont be afraid of it, its an incredibly useful tool........I will ne honest with you here, if you dont want to use it you dont HAVE to, but you arent gonna have fun with linux without it