How to Reinstall OS X on Your Mac
If a problem has truly brought your Mac to its knees, it may be time to reinstall your favorite operating system. It’s bad enough that you have to suffer through the hassle. You’re understandably panicked about retaining files and user settings.
Remain calm. Then do the following, if you have an installation disc and optical drive (which, frankly, is going to cover an older version of the operating system):
Insert the OS X installation disc into your CD or DVD drive.
When you’re asked to do so, choose your current OS X disk as your destination disk (which in all likelihood is your only option anyway).
You’ve arrived at an important point in the process.
Do one of the following:
If you want to salvage existing files and settings, select Archive and Install, and then select Preserve Users and Networks Settings.
If you prefer starting anew, select Erase and Install, keeping in mind that you can’t undo this action, so existing files and settings may as well be toast.
To install certain parts of OS X, click Customize; to perform Apple’s recommended basic installation, click Install.
Because the OS X disc you have may not have all the latest tweaks, pay a visit postinstallation to Software Update (choose it from the app menu) to bring Snow Leopard, Lion, or whichever version of OS X you’re using up to date.
A retail version of OS X may differ some from the version that was loaded on your computer.
Don’t reinstall an earlier version of OS X over a later one. If for some reason you feel compelled to do so, however, first erase your hard drive completely or select the Erase option in the OS X installer. You’ll have to reinstall any software updates.
But what if you don’t have an installation disc? That’s indeed the scenario with Mavericks, because the current flavor of OS X eschews old-fashioned installation methods. Apple has a built-in recovery disk feature that not only lets you reinstall OS X, but also enables you to do so while keeping other files and settings intact. Here’s what to do:
Make sure that you’re connected to the Internet.
Press cmd+R when the computer restarts to summon OS X Utilities.
Select Reinstall OS X in the list of options that appears onscreen.
Note your other options in the OS X Utilities section. You can restore from a Time Machine backup, get help online, or visit the Disk Utility toolshed.
Click Continue, and follow the onscreen instructions.
If you’re running OS X Lion or Mountain Lion, you can create a recovery disc on an external drive that will serve the same purpose as the built-in Recovery tool. Make sure that the external drive has at least 1GB of free space, and download the Recovery Disk Assistants. Follow the onscreen instructions from there.