if i disconnect Wifi then system get hanging.
I assume you are using Fn + F8 to enable/disable the WLan.
Right?
Did you try to recover the system in order to check if this is a system problem?
I think you should do that and should recover the notebook using HDD recovery procedure…
Power up the unit, press F8, choose Repair my Computer, choose HDD recovery and follow the instruction on the screen… then you will get the system with factory settings.
Then test the WLan.