What ISP do you have service through that states specifically in their contact that you aren't allowed to use a wireless router? That is a bunch of garbage, as you hardware is not their concern.... If that truely is the case, I would tell them to send a tech free of charge to configure my network...... lol... oh well...
I saw previously, that the Wii has an USB adaptor to connect to a PC directly, but what about an ethernet cable... does the Wii have an RJ-45 port on it?