My macbook pro will not boot up all the way. the computer keeps shutting off when its starting up. i get the apple icon and then a bar comes up at the bottom and looks like its loading something...then stops...then loads again and then shuts off. i took the battery out and then tried it again and the same thing happens...it doesnt start up at all, could it be firmware? if so...is there a way to restart the firmware? let me know because i have important files i need to retrieve.. 