The problem that you have is your have bought a switch. A switch will not work. You should have bought a router. e.g. Netgear DG834. So that is what you need to do buy a router.
If you modem does not have an Ethernet output you may be better off buying a router with a built-in Modem. In fact they are better anyway as they are much easier to set up.
t
September 2007