You can use WiX to create Windows Installer packages from XML files. This software is available from Microsoft under the Common Public License. For more information about WiX, or to obtain the latest version of the WiX tool set, see Windows Installer XML (WiX) toolset.

We have recoded all the diagnostics registry entries from each Exchange component to a separate component in WiX. This change allows for more control over individual configurations in each update rollup package. The default setting for each diagnostics registry entry is to always overwrite previous registry configurations. This behavior is similar to that of Exchange 2007 Service Pack 1 (SP1) and the original release (RTM) version of Exchange 2007.

Although update rollups overwrite most previous configuration settings, the following registry entry is not overwritten by update rollup packages:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeServiceHost\RpcHttpConfigurator

Default value: PeriodicPollingMinute=15

If you customize this registry entry after you install Exchange 2007 SP2, the registry entry will not be overwritten when you install an Exchange 2007 SP2 update rollup package.

Note:
If you delete this registry entry after you install Exchange 2007 SP2, subsequent update rollup packages will reinstall the registry entry together with the default value.

Exchange 2007 SP2 introduces five stub components to provide registry settings for each server role. These stub components can be used by subsequent update rollup packages. By default, future update rollup packages will not overwrite the configurations for Exchange components. However, if future update rollups require new configurations and if the configurations can be customized by users, the new stub components can be used to preserve the custom configuration settings during the installation of an update rollup.

For example, SampleComponent has the following settings in Exchange 2007 SP2:

	Copy Code
<Component Id="Configuration" Guid="b8dd2994-1cb4-4339-947e-94955aae3723" NeverOverwrite="yes" ...> <Registry Id="RegConfig1 " Root="HKLM" Key="SYSTEM\CurrentControlSet\Services\MSExchangeServiceHost\RpcHttpConfigurator" KeyPath="yes" Name="PeriodicPollingMinutes" Type="integer" Value="15" /> </Component>

In this example, if the registry subkey does not exist, Windows Installer will create the subkey and assign it the default value during the update rollup installation. However, if all of the following conditions are true, Windows Installer will not overwrite the registry entry:

• The registry key exists.
  
  
• The NeverOverwrite attribute is set to yes.
  
  
• The KeyPath attribute of the SampleComponent registry subkey is set to yes.
  
  

Note:
This design change has a limitation. Because only a few stub components are available for each Exchange server role, we cannot add new components or new folders for an update rollup.

In earlier update rollups, some non-versioned files, such as .ps1 scripts that were modified by the update rollup, were not changed back during the removal of the update rollup package. This behavior occured because of a problem in earlier versions of Windows Installer, which did not correctly restore earlier copies of files. Because of the limitations in earlier versions of Windows Installer, Windows Installer 4.5 is required to install Exchange 2007 SP2.

For more information about how Windows Installer handles file versioning, see File Versioning Rules.