How to reconfigure my Linksys router WRT54G2

Hello, I have a 2yr old Dell Inspiron 1525 laptop with Vista and I have not been able to connect to the net wireless for a couple of weeks, I keep getting a pop up window saying that the Dell Wireless WLAN card has stopped working. I have talked with Dell techs multiple times and they have ran every diagnostic possible and they say that the WLAN card is working fine that it is either the cable connection or the router. I called Optimum cable and they too ran diagnostics and said it's not them. Today I called Linksys and they said that the router has to be reconfigured but that since the router is 2yrs old, I am no longer under warranty and they want to charge me $30. I have been unemployed for over a year and I really do not have the spare money for this. I am on the internet wired but I can't move the laptop.
Can someone help me to reconfigure the router? I have already reset it by pushing in the little button for 15 seconds. Now what?

Any help here would be greatly appreciated

Thanks