cannot connect desktop to router and dsl modem

I was using cable modem to connect a wireless d-link router, and then to my desktop and laptop. It worked fine.

Now I changed the ISP and I am using DSL. When connect desktop to dsl modem directly, it works fine. But when I add the d-link router between them, the desktop just cannot detect the connection and shows unplugged. The wireless works fine so I can connect the laptop through router and dsl modem. The weired thing is that I can even connect my laptop by a cable to the d-link router and it also works. I checked the cable, the dsl model configuration, and the router configuration, but do not see anything wrong. Can anybody help me? Thanks. As the last solution, should I re-install my desktop?