Ethernetcard: I do have the same card, when I purchased it came with a MsDOS diskette, containing software to configure it, e.g. for full duplex. There were some more for me incomprehensable options, which I did not touch of course.
If you don't have MsDos on your (modern!) computer: booting from a MsDos installation diskette and interrupting it to MsDos at the indicated moment (you will see on your screen) will do. Then replace the MsDos installation diskette with the Net-installation diskette. Don't install the supplied Linux driver, it is far too old. But useful are: the netcard configuration and the network testing software. Maybe full duplex is useful if you are playing games over the local network in a competition between several workstations. Don't expect wonders. As I am only internetting, and using a hub (Edimax 100 Mbps Network Starter kit), I did not bother to install Full Duplex. As a consequence I do not know if the Linux ethernet-driver supports Full Duplex.
My cable modem, connected to the Freesco router, is 10 Mb only and I bet half duplex.
Mandrake & Suse come with elaborate install & configuration proggies, Slackware not!! Therefore it is so small & fast. I know only two shell-files that assist you: /sbin/netconfig to install (only one!!) ethernet card and /usr/X11R6/bin/xwmconfig that is handy if you boot your Slackware in console mode. It gives you the opportunity to set up which WindowManager starts if you issue a startx to start XWindows. Default is KDE, but Gnome and several others are installed are easy to start so. You should study the source, to see which dirs have to be present in your home-dir and it is easy to add a downloaded window-manager for a tryout. (e.g. Ratpoison).
If you change as superuser in file /etc/inittab the line
and reboot your computer starts in consolemode (as real linuxers do :-) ). Login as root and give the command
You come into a very comprehensable text-menu.
man adduser gives more info.
(Of course this can be done in an console under X-Windows).
Welcome to Slackware config file editing in console-mode in /etc (and other dirs) !! Read HOWTO's & mini-HOWTO's.
Sound: I use the Alsa drivers (0.9.x) from www.alsa-project.org
Final remark: a nice way to accelerate things is to edit the files in /etc/rc.d (just comment out what you don't need) and build your own kernel.
Hope this helps a bit.