In Mac OS or Mac OS X, what should I do if a blinking question mark briefly appears when I restart my computer, but then it continues to start up normally?

While starting up, if your Mac OS or Mac OS X computer briefly displays a blinking question mark, possibly alternating with the Mac OS face icon (but otherwise appears to be running fine), chances are you have not chosen a startup disk. In this case, the computer is taking a moment to locate its system software. To fix the problem, follow these steps:

Mac OS X

1. From the Apple menu, select System Preferences... . In System Preferences, from the View menu, select Startup Disk.
   
   
2. In the Startup Disk preference pane, select the volume and/or operating system you want to start from by clicking its icon once.
   
   
3. Restart your computer. When the computer restarts, there should no longer be a delay before the normal startup process begins.

Mac OS 9.x or earlier

1. From the Apple menu, choose Control Panels, then select Startup Disk.
   
   
2. In the Startup Disk control panel, select the volume that contains your system software by clicking its icon once.
   
   
3. Restart your computer. When the computer restarts, there should no longer be a delay before the normal startup process begins.

Also see:

• What are the major differences between versions of the Macintosh operating system?
• On my Mac, what do I do when a disk icon with a question mark is blinking on my screen?