Windows Installer 4.5 versions

As you all may already know the final release of the Windows Installer 4.5 Redistributable and SDK are now available.

The current version of Windows Installer is in the form; We have received a few questions regarding the differences in the "build" and "update" fields of the version of Windows Installer 4.5 installed across different supported Windows Operating Systems . I will try to explain what these differences are and why they are expected.

The Windows Installer 4.5 redistributable can install on the following Windows Operating Systems:

Target Operating System

Windows Installer 4.5 version

Windows Vista RTM


Windows Vista SP1, Windows Server 2008


Windows XP SP2, Windows XP SP3, Windows Server 2003 SP1, Windows Server 2003 SP2


Windows Vista RTM build number is 6000, while Windows Vista SP1 and Windows Server 2008 RTM are build number 6001. Hence, to comply with the different OS build numbers and applicability logic on Vista RTM and Vista SP1/Server 2008 operating systems, the Windows Installer binaries are built from the Vista RTM and Vista SP1 servicing branches respectively.

The "update" field is based on the OS revision number.  Since the redistributable packages to install Window Installer 4.5 on the different target operating systems are built from different Windows servicing branches, the revision number is different for each.

However, the different versions have no effect on the functionality provided by Windows Installer 4.5.

[Author: Zainab Hakim]
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