To see current settings (Slackware 9.x):
Use one of the following tools to network adapter to Full Duplex mode:
To set network adapter diferent mode open "Properties" of card in "Network settings" and use "Configuration" button. In tab "Detail" [?] set item like "Media type" to "10Mb Full Duplex".
When you are loading module, add parametrs options and full_duplex. For example with module for NIC 3c590*: