How do I upgrade or reinstall Mac OS X? (Snow Leopard & Earlier)

This is a mini guide on how to upgrade or reinstall your operating system. For more information please check www.apple.com/support or the install guide on your operating system disc. This article is for users who are upgrading their operating system to the newest version as well as users who need to reinstall their operating system. If you are reinstalling the same operating system that you currently have on your computer, you can skip to step 3.

If you are upgrading to OS X 10.7 Lion or later, readwww.tekserve.com/faq/oscomp

Note

You cannot install an operating system that is older than the one that came on your computer originally. For example, if your Mac came with Mac OS X 10.5 Leopard, you cannot downgrade to 10.4 Tiger.

1. Check the system requirements. Every operating system has minimum requirements that your computer must meet. Check the side of the retail box or included documentation to see if your computer has enough RAM, hard drive space, and a compatible processor. Even if it meets the requirements, you may not be happy with the performance—we find that installing the latest operating system on a Mac that’s more than four years old can result in a poor user experience.
2. Check your current software. Some software will work with a new operating system and some will need to be upgraded to continue working. Go to the website of your software manufacturer to see if an upgrade is necessary to run on the latest operating system. Some software manufacturers may charge for updates and some older software may not be available for a new operating system at all. For example, OS 9 Classic is not supported in Mac OS X 10.5 Leopard and later. After you upgrade, you will no longer be able use any OS 9 applications. You also need to check for new drivers for your printers, scanners, and any other third-party peripherals you plan to continue using.
3. Backup your entire computer. Although many operating system upgrades go off without a hitch, it is better to be safe than sorry. We suggest using a backup application and external hard drive to create a complete bootable clone of your hard drive. That way you have absolutely everything from your computer in case a file is lost, gets corrupted, or the install fails. If you value your data, back it up before you continue. See "How to Create a Bootable Clone Backup".
4. Clean house. Take a few moments to organize any files you have laying around, delete unnecessary items, and empty your trash. Disconnect any external hard drives or peripherals. You should only have a power cord, mouse, keyboard, monitor, and Internet connected at this point.
5. Update. While connected to the Internet, go to the Apple menu in the upper left corner of your screen and choose Software Update. Install all the Apple updates available and restart your computer. (This is to make sure that you have the latest Apple Firmware updates for your computer.)
6. Insert the OS X DVD that you want to install. After a few moments the disc will mount on your desktop. Double-click the Install Mac OS X icon and then click Restart to begin. If you don't have a working system installed on the Mac, insert the disk while the Mac is on. Then restart the Mac and hold down the "c" key immediately after you hear the Mac bong. (This tells the Mac to start-up off the disc.)
7. First you’ll be required to choose a language. The Installer will show instructions, read them and then click the Continue button. Then you will have to agree to the software license. The Installer will scan your computer and ask you to select your hard drive but don’t click Continue yet!
8. This next step is specifically for installing Mac OS X 10.5 or earlier, if you are installing 10.6 or later, then Apple has made the installer simpler and you should skip to step number nine. OS X 10.2-10.5 Only: Options—in the lower left corner of the select a destination screen is an Options button. Click it to choose one of the following.

1. Upgrade Mac OS X: Use this option if you are working on an older version of OS X and would like to upgrade. This upgrades your system software, while preserving your personal data.
2. Archive & Install: Use this option when you are having software problems and would like to try to resolve them without reinstalling everything. This option moves your existing system files to a folder named Previous System. A new copy of Mac OS X is installed, replacing the now-archived system files. Make sure you select the checkbox labeled “Preserve Users and Network Settings” so that the Installer knows not to touch any of your personal data. If this sub-option is not selected, the Installer will archive your user data too and install new user folders. Remember that archived data is still accessible and still on the hard drive but is not in active use. Some peripherals and applications may not work after an Archive & Install and you will have to reinstall them.
3. Clean Installation or Erase & Install: If you have already tried an Archive & Install to solve your software problems or want to cut to the chase, you are ready for a clean installation. This option erases the hard drive and installs a completely new version of Mac OS X. WARNING: Your data, applications, and settings (everything on this drive in your computer) will be completely erased! You will need to reinstall all of your extra applications from their original discs and reintegrate all of your personal data from a backup copy somewhere else. If you do not have the restore discs that originally came with your computer, you may also lose all the free software that was included with your computer (iPhoto, iMovie, and others).

9. Customize (Optional). After you’ve chosen your install type and clicked Continue you can choose to customize the installation. Most users will just continue and allow the operating system to do an easy install with all of the normal files. However you may want to slim down your install by choosing the customize button. Mac OS X 10.5 Leopard installs about 5.3 GB of printer drivers, additional fonts, and foreign languages. If you don’t think you will need some of those items, deselect their checkboxes before clicking the Upgrade button.
10. Let the games begin! Hit Install to be on your way towards a new operating system. Make sure your computer is plugged into an outlet and let it do the work. Installations can take quite a while.
11. Update again. Once you restart with the newly installed OS X, you’ll want to do another update. While connected to the Internet, go to the Apple menu in the upper left corner and chose Software Update. Install all the updates available and restart your computer if required. Then check Software Update again until you’ve installed them all.

Published March 24, 2009 12:00 PM
Last modified on November 25, 2011 12:59 PM