hey.... try swithing off your modem and and unplug it and keep it on a rubber/wooden surface for 1 hour then put it back where it was... dont switch it on... switch on the PC... make sure the modem is off and is not kept on a carpet/mat.... then when the comp starts, switch on the modem...
then goto start>run and then type "ping 192.168.1.100 -t" that gateway IP is the one wich the BSNL guys put... plz check ur gateway IP and then hit enter... if the ping returns data... then there is absolutely nothing wrong with ur modem...
then do a ping on the DNS server....
also please check the status of *192.168.1.1
username: admin
pass: admin or password
i dont know about ur modem interface... but check if there are any green/yellow/red lights...
if there are plz tell me... then i'll tell you what to do..
usually the first process works for my huawei modem.....