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Evaluating Differences Between an Upgrade and a Clean Installation

Updated: March 28, 2003

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

During an upgrade, existing user settings are retained, as are installed applications and application settings. During a clean installation, the operating system files are installed in a new folder, and you must reinstall all of your applications and reconfigure user preferences, such as desktop and application settings.

The biggest benefit of an upgrade is that you can accommodate heterogeneous hardware and software configurations without having to customize individual computers in your organization. Also, because an upgrade does not affect applications, files, or settings, you do not have to spend time configuring computers or installing applications during a rollout, which speeds up the deployment process. Another benefit is that you do not need to migrate user data before an upgrade.

The biggest benefit of a clean installation is that all of your systems can be deployed with the same configuration. If you use the same answer file for all your systems during a clean installation, all applications, files, and settings are reset the same way, which means all of the desktops or servers in your organization can be standardized. In this way, you can avoid many of the support problems that are caused by irregular or inconsistent configurations.

You can use the following guidelines to determine whether to perform an upgrade or a clean installation.

Choose a clean installation if:

  • No operating system is installed on the destination computer.

  • The installed operating system cannot be upgraded to Windows XP Professional or Windows Server 2003.

  • The computer has a multiple-boot configuration that needs to support the current operating system and either Windows XP Professional or Windows Server 2003.

  • You are planning on implementing a managed environment through Group Policy, the Active Directory® directory service, or other means, but you have not yet implemented a managed environment. In this case, clean installations are desirable because they ensure that you have a standard configuration on which to implement your managed environment.

  • You want to reset the desktop or server configuration in your organization to a consistent, known standard.

  • You are purchasing new hardware or software as part of your deployment.

Choose to upgrade if:

  • You already have a Windows operating system that is suitable for upgrading, and your IT department centrally manages the computers in your organization.

  • You want to use existing hardware and software, and you do not want to reconfigure user settings, operating system settings, or application settings.

  • You need to retain hardware or software settings for compatibility reasons.

You cannot use a distribution share to perform an unattended upgrade installation. You must use the product CD. Also, the Windows Setup program reads only a limited number of answer file sections and entries during an unattended upgrade installation. For more information, see "Performing an Unattended Upgrade Installation" later in this chapter.


  • Installing multiple operating systems on the same partition is not supported, and doing so can prevent one or both operating systems from working properly.

For a worksheet to help you record information about your installation, see "Unattended Installation Worksheet" (ACIUI_1.doc) on the Windows Server 2003 Deployment Kit companion CD (or see "Unattended Installation Worksheet" on the Web at http://www.microsoft.com/reskit).

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