make sure that you got DHCP enabled in your network properties under TCPIP. If you do go into your cmd line and do an ipconfig /release and then and ipconfig/renew. that releases your ip address and renews it. let me know if that worked
How do you connect to your DSL modem? by Ethernet cable or USB or wireless? If it is wireless then your modem has router built-in, and you shouldn't be worried about the LAN connection (you can disable it by open Network connections, right-click Local Area Connection, choose Properties and clear the check box Notify me when this connection has limited or no connectivity).