Nothing can be more frustrating than turning on your Mac only to find that it won't start up. Instead of seeing the Finder, you see a blue or gray screen, an icon of a broken folder, a kernel panic, a flashing question mark, or a computer that just sits there. What can you do? Don't worry. It could be a simple issue that you can fix yourself.Note: This article applies to Mac OS X 10.3.9 or earlier.Tip: If your computer won't start at all, skip to "You see a blank, gray screen" below.