If eth0 doesn't show up in the ifconfig list it means (hopefully) simply that the interface isn't just configured. There's a tool in Slackware for doing that; I thought it would be just netconfig but if you've run it, then there's something odd with it. As I don't remember what dhcp client Slackware tends to use by default, try running either of these commands:
Code:
dhcpcd eth0
dhclient eth0
and see if that does anything..