My Macbook Pro is frozen on the startup screen. I see the apple logo with vertical blue stripes. I tried to reset the PRAM i.e., I forced it to shutdown. I unplugged the power cord for a full minute or more. I restarted and then held down command(open apple) option and the p-r keys simultaneously after the first chime. I held the keys down till after the 3rd chime. It is still frozen i.e., apple logo with blue stripes and frozen spinner. What next?