Repair a Damaged Hard Disk on Your Mac with Disk Utility
Just about every championship baseball team has a valuable utility player to fill nearly every position. The versatile Disk Utility tool on your Mac serves this purpose for all things hard drive–related and many things optical drive–related. At a glance, it gives you a summary of your drives, including disk capacity, available space, and number of files and folders.
If you suspect that your hard drive is actually damaged (even a reboot doesn’t seem to do much good), run Verify Disk to uncover any errors. If you find any, you must be an administrator to authorize a repair. You can’t repair (or even test) write-protected disks and nonrecordable CDs and DVDs.
The most important restriction is this: Although you can use Disk Utility to test the drive you’re using (and, as you’ve seen, fix permissions), you can’t repair it until you boot from another disc. This disc is most likely your Mac OS X installation CD or DVD, which you will need if you’re using an older version of OS X.
With that in mind, it’s a good idea to make a copy of your installation disc right now and stash it in a safe place. (On newer systems with Mountain Lion or Mavericks, you no longer have a disc to install the operating system.)
After booting with this other disc, open Disk Utility, select your startup disk, and click Repair Disk. Incidentally, booting from the other disc is somewhat tricky. To do so, hold down the C key and wait until OS X boots. Make a language selection, and choose Disk Utility from the menu.