post the output of "lsmod" if you like, maybe someone can spot a network module...
as for the usage of modprobe, do a "man modprobe" and you will have all the info you need... basically it's just a matter of issuing the command followed by the name of the module... for example:
the above command would load the module for people with RealTek 8139x network card chips... look in your
/etc/rc.d/rc.modules file for other examples (there's a few 3coms in there)...