1) You should indicate in your LQ profile or inside your post what are your distribution and version. For now I suppose it is Slackware 12.2. Please confirm that.
2) There is nothing you need to uncomment in rc.modules. Your card should be recognized and the module and firmware loaded at start up, provided you did a full install of Slackware 12.2, including the iwlwifi-3945-ucode package which installs the firmware for your card.
3) You can check if the module iwl3945 is loaded with 'lsmod|grep3945'. otherwise 'dmesg|less' to see why it is not.
4) You card should show in 'ifconfig -a' output as well as in 'iwconfig' output
5) You should edit /etc/rc.d/rc.inet1.conf to include your network parameters and make sure both /etc/rc.d/rc.inet and/etc/rc.d/rc.wireless are executable.
6) Read Configuring your network in Slackware
from Alien Bob for more information.