I have a ASUS K43S laptop having windows 7 64 bit OS in it.

From today morning I am not able to access internet using wifi. Its look like I have accidentally deleted the WIFI driver.

Please note:- Even after pressing Fn(Key) + F2(key), Wifi indicator light is not making on.

Please advice.

Check your devices to make sure they are all installed and working.
Head over to Asus's site and grab any drivers you might need.