The Macintosh operating system comes with a utility built-in called Disk First Aid. The purpose of Disk First Aid is to check the integrity of a drive you select to make sure that the contents of the disk are free of errors. If any found errors cannot be corrected by Disk First Aid, third-party software applications are available that may be able to fix issues that are found.

To Use Disk First Aid:

1. Close all running applications.

2. Hold down the COMMAND key (otherwise known as the Apple key) on the keyboard, and then press the f key. This launches a utility known as Sherlock.

3. In the white box, type Disk First Aid, and then press the Enter key.

4. Select the drive you wish to check by clicking on it, then click on Verify. This checks the integrity of the drive for problems.

5. If any errors are found on the drive, you will be notified of the results. If errors are found, click on the Repair button.

6. You can save a text file of the Disk First Aid report by clicking on File in the top menu selection, and selecting Save Results.