Help with pc settings for wireless router

Hello,
I wiped my operating system and reinstalled all the software and operating systems windows xp, but I did not save the settings in networking connections pc runs great when hooked to modem but when i hook the modem to the router wrt54g ver.2 and router to the computer it will not connect to the internet. Verizon tech support through remote access was able to communicate through router to computer, but would not help with settings Linksys support will not help without paying for support because warranty has expired. the fee is as much as a new router. How can I set my network connections so I can use my router again. PS when I installed disc i can get as far as checking internet connection no connection found so only can go on internet through modem only.