Ok the issue is solved... The problem was that my program was not being able to find the IEEE 802.11 wireless network interface... Since the dawn of Vista, Windows has changed some it its architecture and my program was made years before that...
Before Vista, the network adapter type value for Ethernet and IEEE wireless was same i.e 6
and is known as MIB_IF_TYPE_ETHERNET
... But now they both have been differentiated and IEEE wireless adapter gets a new value 71
... In our code we had a validation to reject network adapters other than MIB_IF_TYPE_ETHERNET
and so it used to work with XP, but Windows 7 had other plans... Adding another validation for IF_TYPE_IEEE80211
solved the problem.
You can check out the below link to get more clarity over this and let me know if you've any queries... IP_ADAPTER_INFO structure (Windows)