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Office Communications Server 2007 R2 Enterprise Edition Install Application Host Fails

I am trying to install Office Communications Server 2007 R2 on a Windows 2008 Server Standard install but I'm getting stuck when it tries to install the application host. I originally tried this on a 2008 R2 server but I got stuck at the same place. I am stuck at Step 1 of Add Enterprise Edition Server to Pool. After clicking Run to add the server to the pool I get the following error:

[0xC3EC796A] MSI installation was unsuccessful. Please check the log file for more information.

Inside of the log file, the following error is listed:

MSI (c) (30:D4) [12:52:50:318]: Windows Installer installed the product. Product Name: Microsoft Office Communications Server 2007 R2, Application Host. Product Version: 3.5.6907.0. Product Language: 1033. Installation success or error status: 1603.

I have spent the last 3 days trying to find out what's causing this error. There is nothing in the Event Logs. Am I missing something?
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BusbarSolutions Architect

I think that the installation file is corrupted can you try another ISO


I just re-downloaded the ISO and it's still giving the same error.
Most Valuable Expert 2015

Many failed OCS installations are caused by an Interfering Windows Update. First in "Programs and Features" of your Control Panel remove KB974571, Reboot, then run the Patch below (ocsasnfix.exe):


After that reboot again, and now try resuming the OCS installation.


Removed update, reboot, ran patch, reboot then reran OCS and ran into the same issue.
The problem was with a group policy blocking something. Not exactly sure which policy was affecting it, but blocking inheritance for all policies allowed the installation to finish.