problem replacing dlink 604 (wired) router with wireless

Hi All Equipment: dsl modem= Speedstream 5360 current router = Dlink 604 (Wired) ISP = Sbc Yahoo DSL Problem: when i remove the 604 and try to connect modem directly to PC the PC cannot commumicate with internet. All lights on modem and nic show connection and when i try to go to web page the activity lights flash but i always get a "cannot find server" error message. I discovered this problem when I tried to replace the 604 with a wireless router and got same result. so i attempted to remove the router (604) and just go dsl modem to PC. Before I installed the 604 I had cable directly to pc from modem. however I have upgraded PC since then. I have attempted bypassing the 604 with both my laptop and desktop. Same results on both. I have tried 2 wireless routers and the direct connections method mentioned above and the only way i can get on the inet is through the