General advice on performing an Archive and Install
This FAQ is a subset of the comprehensive advice in the "Archive and Install" chapter of our book, Troubleshooting Mac® OS X. It addresses the basics of performing an Archive and Install to restore the System-level components of Mac OS X
For additional information concerning Archive and Install, see the "Archive and Install" chapter of Troubleshooting Mac® OS X.
Why use Archive and Install?
The Archive and Install installation option is used to replace the System-level components of Mac OS X while offering an additional option to preserve both the Users folder and network settings. This is as opposed to an Erase and Install which erases the hard drive before installing Mac OS X.
After performing an Archive and Install you can either bring your system back to the most current version of Mac OS X via Software Update, or downgrade to an earlier version of Mac OS X by installing only the desired standalone updates. 
Who cannot use Archive and Install?
You cannot perform an Archive and Install if you have Mac OS X Upgrade CDs: you will need the full retail package of the version of Mac OS X you are using. In particular, you cannot perform an Archive and Install if:
- You installed Mac OS X 10.3 Panther® using the Mac OS X v10.3 Upgrade CDs and you have also installed the Mac OS X 10.3.1 or subsequent Update. Instead, you will need to employ the process specified in the AppleCare® Knowledge Base document Mac OS X 10.3: Reinstalling from a Mac OS X Panther Upgrade CD.
- You installed Mac OS X 10.2 Jaguar using the Mac OS X v10.2 Upgrade CDs, which lack the Archive and Install option. You will need to reinstall Mac OS X 10.1.x first. See the AppleCare Knowledge Base document Mac OS X: How to Reinstall a Prior Version.
Performing an Archive and Install
You will need...
- One of the following sets of discs corresponding to the version of Mac OS X you will reinstall via Archive and Install:
- The full Mac OS X v10.x Retail Package DVD or CDs of the version of Mac OS X you plan to reinstall.
- The installation CDs or DVD that were included with your Mac if the version of Mac OS X you plan to reinstall is the same version that was originally installed at the factory.
- Note: In the Procedure below, the disc labeled Install Disc 1 from any of the discs listed above will be referred to as the Mac OS X Install Disc.
- Sufficient free or available disk space for a second, full installation of Mac OS X on the volume on which the Archive and Install will be performed. The available space should meet the value specified for available disk space in the system requirements for the version of Mac OS X to be reinstalled. This is generally: 5 GB for Mac OS X 10.4 Tiger® and earlier; 9 GB for Mac OS X 10.5 Leopard®.
- The following AppleCare Knowledge Base documents:
Delete the Previous Systems folder.
- Familiarize yourself with the Archive and Install process:
- Print and review a copy of the AppleCare Knowledge Base document "Mac OS X: About the Archive and Install Feature."
- We also recommend that you print and review the linked documents cited in the Related links section of this FAQ corresponding to the version of Mac OS X you are using.
- Assure your hard drive is in good order.
- Before performing and Archive and Install, start up your Mac from your Mac OS X Install Disc and run Disk Utility > Repair Disk to assure there are no problems with your hard drive: there's no point in reinstalling the operating system before correcting any potential hard drive corruption. For step by step instructions, see Steps 1 and 2 of the Procedure in our "Resolving Disk, Permissions, and Cache Corruption" FAQ.
- Perform the Archive and Install.
- Follow the instructions in the AppleCare Knowledge Base document "Mac OS X: About the Archive and Install Feature." Be sure to select the "Preserve User and Network Settings" option to preserve your current Users folder and related network configuration.
- Install the Mac OS X Combo Update corresponding to the version of Mac OS X you were running before performing the Archive and Install. 
- Assure your third-party applications are running properly.
- Third-party applications you have installed in the Applications folder are copied intact to the Applications folder of the new Mac OS X installation. Likewise, the Macintosh HD > Library > Application Support folder is also copied intact as many third-party applications install components in this folder.
- Nevertheless, some third-party applications may not work after performing an Archive and Install. This is cited in item 2 of the "Tips and notes" section of the AppleCare Knowledge Base document "Mac OS X: About the Archive and Install Feature":
- 2. Some third-party software items may not be preserved. If third-party software doesn't work after the Archive and Install is performed, reinstall it or contact the vendor.
- In particular, third-party application components that are installed in the folders
- Macintosh HD > Library (other than the Application Support folder therein)
- Macintosh HD > System > Library
- will not be not be preserved. Examples include third-party Startup Items and kernel extensions.
- Therefore, it is important to test all of your third-party applications to assure they are running properly after an Archive and Install. Third-party applications that do not work correctly may need to be uninstalled, then reinstalled. See also:
- The AppleCare Knowledge Base document "Applications don't work after reinstalling Mac OS X."
- If reinstalling Mac OS X 10.2, the article Migrate to OS X 10.2 with a Clean Install from the October 2002 issue of Macworld. While this article was written to advise users upgrading from Mac OS X 10.1.x to 10.2, the additional details it provides on Archive and Install may prove useful when reinstalling Jaguar.
- Once you are satisfied your system is operating properly, delete the Previous Systems folder. The Previous Systems folder can be found at the top level of your startup disk, i.e. the Macintosh HD > Previous Systems folder. To delete the Previous Systems folder:
- If you are running Mac OS X 10.3 or later, log in to the Admin account and drag the Previous Systems folder to the Trash. Type your Admin password if prompted. Then empty the Trash.
- If you have problems with this method, you can also use the procedure described in the AppleCare Knowledge Base document "Mac OS X 10.2: How to Delete a Previous Systems Folder."
- If you are running Jaguar, employ the procedure defined in the AppleCare Knowledge Base document "Mac OS X 10.2: How to Delete a Previous Systems Folder."
 Apple does not recommend performing "downgrade installs" as specified in the AppleCare Knowledge Base document "Mac OS X: Troubleshooting installation and software updates." However, by using Archive and Install, installing the Mac OS X Updates or Combo Updates to bring your Mac to the desired version of Mac OS X, and deleting the Previous Systems folder it can be done.