None of the options have helped for me. I am able to start up the computer, I hear the chime and it is a white screen. No logo, processing circle, nothing. The only one of the suggested restarts that had some type of response was the NVRAM, the screen would go black and chime over and over again until I released the "Command+Option+P+R". I am unable to identify if the disck is full, or anything. HELP!