If your computer won’t start up normally, you may need to use a disk repair utility to fix the issue. Mac OS X includes two utilities for this—Disk Utility and fsck. You can also use these even when your computer starts just fine but you want to check the disk for possible file system issues. For Mac OS X 10.4.3 or later, check out “About live verification in Mac OS X 10.4.3 or later”. Apple Care