BSNL is renowned for its frequent problems and bad customer support, but do not fret if you have a DSN problem where all the lights on your modem are blinking but still you are unable to access any website or web-page.Here is a simple fix-
Open the "Network and Sharing Center"
Open "Manage Connections"
Open "Properties"
Click on "IPV4......", there choose the option, "Use the following DNS servers instead".Enter the two values as -
208.67.222.222
208.67.220.220
These are OpenDNS.You will be able to browse internet without any hassles now.
Recommended Read - BSNL Noisy Line Problem Fix.