To my knowledge, in Slackware 'Network settings' (the 'netconfig' command) works only for eth0 and can't handle wireless settings such as WEP or WPA -- that you do not need for now, hopefully.
All network settings are kept in the file /etc/rc.d/rc.inet1.conf that you can edit by hand. And, the file /etc/rc.d/rc.inet1 should be made executable:
chmod +x /etc/rc.d/rc.inet1
so that your computer be connected after booting.
You will find all information you need about network configuration in Slackware in this article
from Alien BOB.
In a pinch, if your wireless card's interface name is wlan0 (you can check that with 'ifconfig -a' and 'iwconfig') you could use following settings in /etc/rc.d/rc.inet1.conf (just uncomment appropriate lines):
You should be connected. At next start the script /etc/rc.d/rc.M which source /etc/rc.d/rc.inet1 will do a '/etc/rc.d/rc.inet1 start' so you will be connected.
PS Please get rid of Ndiswrapper that you do not need, go back to the native Linux driver as it works.
PS2 I suppose your server uses dhcp protocol to allocate IP addresses. If not, set configuration parameters in /etc/rc.d/rc.inet1.conf for static IP. I guess you know how to do that