Unable to access Internet

Hey all,

I have a ADSL Connection from my Local ISP Airtel, the problem is that i am unable to access the internet, i am able to ping to my Default Gateway and login to it, am not getting any reply from primary and alternate DNS server, i see all the LED’s blinking(Power,Link,Data,PC/USB)
the ADSL modem/router which i get from my ISP is Beetel 220bx ADSL modem. i also have Zonealarm Firewall and security suite i have tried to Shutdown the firewall but still cant access the Internet. lol i have also reinstalled ma LAN card drivers but no avail evryhting seems to be good but cant access the net.
Please HELP ME.
Thanks and Regards
Bhanu Prasad