On my Mac, what do I do when a disk icon with a question mark is blinking on my screen?

If you see a disk icon with a blinking or flashing question mark when you try to start your Mac, your computer was unable to identify a startup disk that has a working copy of the operating system on it. This problem can be caused by either hardware problems or corrupt software. To find out which it is, try to boot your computer from the DVD or CD that came with your computer:

1. Insert the system disc into the CD or DVD drive and restart your computer while holding down the  c  key.
   
   
2. Once your computer has finished booting, release the  c  key. When the menu bar appears, from the Utilities (Mac OS X 10.5), Disk Utilities (Mac OS X 10.4), or Installer (Mac OS X 10.3) menu, select Disk Utility.
   
   
3. In the column on the left, select your hard drive, and then on the right, click the First Aid tab.
   
   
4. If the Disk Utility cannot recognize your hard disk, you may have a hardware problem. Contact your nearest Apple certified repair shop.
   
   
5. If Disk Utility does recognize your hard disk, have it try to repair the problem. If it can't, you'll probably have to reinstall your system software. In some circumstances, you may have to format your drive and start from scratch. If you do this, however, you will lose anything you have on the hard disk. For instructions, see How do I install or upgrade Mac OS X?

For more information about this problem, see Apple's knowledge base.

Also see:

• In Mac OS and Mac OS X, what does the startup icon mean?
• In Mac OS and Mac OS X, what is the PRAM, and why would I want to zap it?
• On my Macintosh computer, why can't I format or partition the internal hard drive?
• For Mac OS X, what are some useful utilities for troubleshooting and optimizing performance?