Laptop to Router WRT54G – no internet connection

When I try to configure my laptop to a certain wireless router WRT54G, I don’t notice any light on the ports although I notice other lights. Why is it so?
I have tried to reconfigure the router to the laptop after having all the cables unplugged but this had no impact at all as I still get the message stating that there is no internet connection available. I am starting to wonder if this is due to a reinstallation of Windows Vista that I did some time back then because the problems developed since then. Please help.
