I need to reformat my MacBook because it has in past week begun crashing constantly and no longer loads OS X. Instead of the gray apple icon at startup I get a blinking folder w/ a question mark. I believe this is due to a previous Vista partition I deleted with much trouble many month ago. In anycase I ran the diagnostic which found no hardware problems, but I have been unable to reformat the computer w/ disk utility as it seem to be unable to recognize that a hard drive exists. Is there an alternative manner in which i could reformat the drive? Or is there perhaps a wa to restore my computer without reformatting?