I configured the belkin router Belkin wireless-n

Connect a LAN cable from Belkin to your laptop/computer's LAN port, open a browser on your laptop/computer and enter the Belkin's configuration URL. http://192.168.2.1
The default PW = blank (just press Enter) You can now change the default admin password.
You can now configure the wireless settings to protect your wireless network and Internet from unauthorized access. Now configure the wireless card in your computer/laptop with the router's wireless settings. To secure your wireless network from unauthorized access, please click on this link and follow my instructions :- http://www.fixya.com/support/r3559128-wireless_router_security

The router's encryption (password) is configured in the router's wireless settings.
Connect a LAN cable from Belkin to your laptop/computer's LAN port, open a browser on your laptop/computer and enter the Belkin's configuration URL. http://192.168.2.1
The default PW = blank (just press Enter) You can now change the default admin password.
You can now configure the wireless settings. Now configure the wireless card in your computer/laptop with the router's wireless settings. To secure your wireless network from unauthorized access, please click on this link and follow my instructions :- http://www.fixya.com/support/r3559128-wireless_router_security

As i understand you have a router provided by your ISP: MTNL, you need to configure the Belkin router in Dynamic mode and not in PPPoE. Then restart the devices by unplugging the power from MTNL router and Belkin. Wait for 20 secs, then power up MTNL router 1st, wait for all lights to get steady and finally power up the Belkin wireless router. Then you will find the modem and internet light lit up properly.
For any further clarifications, revert!

Thanks and regards,
Arvind

Either you have not configure the Wireless SSID or your router is faulty. You can use the easy setup using the CD or configure the router by going to the default IP address. Do read the setup manual first.

It seems like your router is configured once without any issues. Ignore that error message if you are connected with the internet. The setup couldnt find the Network adapter or the router because it is know more a factory default settings. It is been configured already