No internet signal between router and desktop pc.

Question

Linksys (wire-type) Router to Desktop PC (Microsoft XP). DSL to house using AT&T phone line > filter > DSL Cable > DSL Modem > out of modem using ethernet cable to Desktop PC. We added a second Desktop PC, so . with instructions from at&t, purchased Linksys (wire-type)Router . . .now we take ethernet cable from position on modem to WAN port on Router . . .then use ports 1-4 to connect ethernet cable to PC's. While running Linksys's supplied Installer CD . . .when checking connection between router and pc - - -error message indicates no internet signal/data between the two. Cabling hook-up is text book. Please help troubleshoot! Thanks. jg [e-mail]