I have MBP 15 that I can't seem to get booted up. It cycles the optical drive, and I get the chime, Apple logo lights up as well as the backlight on the screen, but the screen remains black. I have reset the SMC, but unable to reset the PRAM (I never get anything beyond the initial startup chime.) To my knowledge, a firmware password was never set. Does anyone have any ideas on what I can try to resurrect this thing? Thanks in advance!