No internet via Ethernet, USB works?

Hey guys-

I am dealing with a network connections problem..

My wife's desktop will not connect via the ethernet port..

My setup is this:

Linksys router with 4 port switch..

I am running the internet into the router and then out to the
desktop..

This computer will work on the internet when plugged straight to the
modem via USB.. However, with the ethernet, it is not working.. and
when I run the USB to the desktop from the modem and then run some
ethernet to the wireless router, it pretty much shuts them both
down..

When the ethernet is plugged into the desktop, the two lights (green
and amber) both illuminate and the amber flashes, signalling that it
is indeed getting traffic, however, when I go to network connections,
there is nothing there...

Anyone have any reccomendations or ideas what may be the issue?

I have tried the "unplug the modem.. turn off the desktop...
reconnect power to modem.. let is sync.. then turn on the desktop...
"

Also, when I go to network connections, there is nothing there and
when I try Control Panel > Network Setup Wizard i get a
"cannot complete" as it says it cannot find my network
hardware?

Is this a driver issue? Is the MoBo not reading the ethernet ports?

If so, anyone know where I could pick up a driver for this?