Unable to connect Wireless issue

Hello,
I am having problem with my wireless router not getting connected to the internet. I have a Wired Broadband internet connection which is connected to my Desktop computer thru a modem provided by ISP. I decided to share internet connection on my other Laptop systems at home using a D-Link Wireless router.
I am not a tech savvy person, and the Broadband cable does not have provision to connect directly to the D-Link Router (Cable does not have a switch but a pin connected to the modem), so I decided to go by simple logic. I allowed my wired cable to remain connected to the modem and then connected the Router to the modem using LAN Cable.
I thought that I am fairing well all these while, but I lose the internet connectivity the moment LAN is connect, and I get a bang (yellow exclamation mark) on to the network in notification area. The IP Address also changes to 169.xxxx.x.x.
I tried configuring my D-Link router from support web site but all in vain. I also tried resetting the router and performing ipconfig/reset & ipconfig/renew, but no go. My wireless connection is not showing in, when I checked in home network and it is showing as no network setup or access. It’s a Desktop with D-Link router and Windows 7 installed. Please suggest.
Thanks in advance.
