My MBP won't boot to mac os. It will show the gray screen then the little gear wheel spinning but that's it. Will just spin. Also it went to the blue screen for a bit then the gear spins some more. It shows the cursor then the gear spins some more. I've tried holding down shift to boot into safe boot but it don't work. How can I fix this? I don't have os cds to put into the cd rom so I need another method. Please help.