I searched all over the net for connecting BSNL NIC in windows 7 but couldn't find a useful link for the same. Finally it was a service center guy who helped me in sorting it out. So i thought of posting it here so that it could be of help for anyone in this community or others.
This is how to install BSNL NIC(u100) in windows 7:
1.Get the u100 windows 7 driver software from the BSNL website.Here is the link-http://bsnlhelpline.blogspot.in/2010/04/cdma-datacard-drivers.html
2.Select the 32-bit or 64-bit version as per your OS version.
3.Select the USB modem installer in the folder. Then the U100 installer window opens.
4.Insert the USB modem when asked in the window. Then it will either show 'please install drivers manually' or 'installation complete'.In both cases, click finish.
5.Now right click computer -->manage-->device manger.
6.Click other devices. Inside other devices, there will be two folders with name 'Data Interface' showing yellow caution signs. Right click one of them and click update driver software.
7.In the window which comes next,choose 'browse my computer for driver software',now browse and select U100 driver windows 7 32 bit/64 bit(as per your OS version) from the location where the U100 driver folder is created. Now click next. Waiting for a few seconds,it shows 'driver successfully updated'.
8. Do the same with the next folder named 'Data Interface'.
9.Now Enter the icon named Modem which appears in the desktop. In the dialler window,wait for the USB modem to get ready and show the modem range on the top. Then click settings, type in your username and password and save it.
10. Now you can dial and get connected.
I think this will help any of those who try to connect BSNL NIC in windows 7.