How about a brute? Is telnet or ssh open?

NjOy,

Manu was recommending to you that you use a tool to brute force guess the password for the router, like Cain and Able, for example.  It should be trivial to crack your password since you should know if there are any special characters, upper case letters, lower case letters, or numbers.

In regards to any vulnerabilities, I was not able to find any information about that router on the internet. 

I do not believe you would receive any additional help other than that from this forum.  It seems a bit odd to me that you would need to access your router because you switched from Windows to Linux.

You may want to try the forum http://www.indiabroadband.net/.

If all else fails, try BSNL tech support at 1800-424-1600.