When I dropped my phone the screen showed some weird colours on upper right corner. I replaced the screen. Now by using the recommended three button sequence the led in upper left corner comes on for a few seconds as well as the home button and the other two lights up and then go out. I call the phone and it vibrates but screen remains black. Can I reset the phone using my PC? How can this be done when I cannot get any response from the screen OR is the mother board at fault?