Download and install this driver: ggsetup-2.2.0.6.exe
Phone have to be OFF when you are conecting it.Remove sim and memory card from the phone.Shut down the phone and remove battery for 5-10 seconds then insert it back but don't switch it ON.Press and hold the C button(don't let go C)then insert USB cable into the phone,try few times but always remove battery for 5-6 seconds and try after that.