SBS 2003 internet problem

I set up an SBS 2003 network this week. DSL modem connected to PCI network card. The onboard network card connected to the switch. Everything worked great. Then my sidekick tried installing a Linksys wireless router by attaching it to the switch and ran the install cd from the servers dvd. Then the internet stopped.

Any idea how i can get the internet back and the network up and running again. Any help would be really appreciated