Look into configuraion on the adsl modem by directly connecting it to the pc and restarting both the pc and the modem, then looking into dhcp - did you get an ip or not, if so the seetings are there, get into the gateway and change the settings as you like, providing you have the password. If you dont get an ip, chances are you have a static ip setup and will need to input that date into your nic yourself, your provider will have the necessary info for you.
If he was using a Linksys Router try to configure web based settings of your Linksys router. To be sure, make it all in default setting, default http for your web based configuration of your router is
http://192.168.1.1. To be sure, check your Linksys manual & model.