It's been a few months now since the Windows Installer 4.5 redistributable was released [link]. Over the past couple months I have received several questions (quite often similar in nature) that warrants this blog post <grin>. In this post, I will attempt to answer some of the most frequently asked questions with regards to adoption & deployment of MSI 4.5.

1.       I’m considering taking a dependency on MSI 4.5 for my next release. I would like to know how prevalent MSI 4.5 might be in our target environments. Do you have any data on this?


We are pleased to hear that you are considering taking advantage of the new feature set and functionality provided in MSI 4.5. We have some data that may help you understand the current penetration of MSI 4.5 in the ecosystem.

a.       Statistics from the Microsoft download center:

As of March 2009, there have been over 5.6 million downloads of MSI 4.5 (combined across all supported platforms & OSes).

b.      Other ways in which MSI 4.5 is being deployed to users machines:

Yes, besides the fact that users are downloading MSI 4.5 from Microsoft download center, there are also other mechanisms via which MSI 4.5 is being deployed to users machines. For example;

-          SQL Server 2008 (both full server as well as express version) requires MSI 4.5 as a pre-requisite.

-          This dependency in turn has a cascading effect on other products that are already dependent on SQL Server 2008 or will be in the future.

c.       Future Windows service packs:

MSI 4.5 will be natively included in all future service packs of Windows. It is already included in Windows Vista and Server 2008 SP2. Release candidate for this service pack is presently available from the Microsoft download center.

2.       When will MSI 4.5 be deployed via Windows Update?


MSI 4.5 will be on Windows Update as part of future service packs to Windows (see #1, part c). It will not be available independently as a required mandatory update like Windows Installer 3.1 v2.

3.       Is it true that there is a forced reboot required on Windows Vista and Windows Server 2008 with MSI 4.5? Unlike Windows XP and Windows 2003, this reboot can't be deferred?


Yes, it is true that servicing Windows Installer always requires a reboot on Vista and above. The new changes made to the Windows Vista servicing stack in combination with the change made by Windows Update to always have the Windows Installer loaded, causes the update to be “pended” until a subsequent reboot thus generating the mandatory reboot requirement when servicing the Windows Installer. We understand that a reboot can be difficult to absorb for applications taking a dependency on MSI 4.5. Unfortunately, none of the solutions that could be pursued were low cost and low risk enough to be acceptable at that point in the Windows Vista SP1 and Windows Server 2008 ship cycle. However, the growing prevalence of MSI 4.5 (details provided in #1), is mitigating the reboot issue to some extent.

4.       We are considering the possibility of bootstrapping Windows Installer 4.5 with our product’s setup. Is there a single 4.5 redistributable that can cover multiple OS versions and CPU architecture that is of a smaller size?


No, there is no single redistributable package to install MSI 4.5. There exist different installation technologies to install a Windows component like Windows Installer on Vista and above OSes versus down-level OSes (Windows XP and Server 2003). Additionally, the binaries itself are different based on OS version and platform architecture.

[Author: Zainab Hakim]
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