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

If your Mac displays a disk icon with a blinking question mark at startup, then it was unable to identify a startup disk with 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, boot from the DVD that came with your computer:

1. Insert the system disc into the DVD drive, and restart your computer while holding down the c key.
2. Once your computer has finished booting, release the c key. From the Utilities (Mac OS X 10.5 and later) or Disk Utilities (Mac OS X 10.4) menu, select Disk Utility.
3. In the column on the left, select your hard drive, and then click the First Aid tab on the right.

   Note: If the Disk Utility cannot recognize your hard disk, you may have a hardware problem. Contact your nearest Apple-certified repair shop.

4. Use Disk Utility to try to repair the problem. If it can't, you'll probably have to reinstall your system software. In some circumstances, you may even have to format your drive and start from scratch; doing this, however, will erase anything you have on the hard disk. For instructions, see ARCHIVED: How do I install or upgrade Mac OS X 10.6 (Snow Leopard)?

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