It should be enabled already, but there are two possible scenarios here so I'll cover them both.
The first possibility is that you did not run the motherboard's or system builder's driver CD when you purchased the Elonex - that is, if this was necessary to complete the installation of subsidiary components. This quite often has to be performed by the user, but not in every case. If this is the case here, then the Ethernet adapter would be listed in Device Manager in an uninstalled state with at least a question mark over it. You can choose to install it - or enable it if it has a cross over it - from here.
Possibility number two is that you simply need to enable the adapter from a Windows point of view. Right-clicking on its entry in Network Connections will show either "enable" or "disable" according to its current state. If it is not present in this folder, then the first scenario applies.
There is a remote third possibility - that the adapter is faulty - but this is quite unlikely.