Exchange Server 2010 Unified Messaging Language Pack installation fails with: “Pending Reboot”

I just finished troubleshooting a problem one of my colleagues experienced with a client where we’re migrating them away from Cisco Unity to Exchange Server 2010 Unified Messaging for voicemail.  The deployment went without a hitch until they made an attempt to install the Canadian French language pack where they would see the following:

c:\temp>Setup.com /AddUmLanguagePack:fr-CA /s:c:\temp

Welcome to Microsoft Exchange Server 2010 Unattended Setup

Preparing Exchange Setup

Copying Setup Files

C:\temp>

They’ve made sure that the UMLanguagePack.fr-CA.exe was unblocked before executing the unattended install, ran the executable to install the language pack interactively but all lead to dead ends.  Since they were out of ideas, they figure it would be best to get another set of eyes on the issue.

I jumped on in the evening and went through all of the steps they’ve tried and reviewed the event logs but none of the logs showed any errors relating to the failed install.  What I did notice with the interactive install was that the details window appears to suggest that Exchange cannot install the language pack because of a “pending reboot”.  This lead me remember a problem I had with a SQL cluster 5 years ago where a pending reboot registry key wrecked havoc when I was trying to fix the MSDTC shared resource.  It’s been awhile since I’ve had to look at the registry keys for pending reboots so I did a quick search on Google and got the following:

http://technet.microsoft.com/en-us/library/cc164360(EXCHG.80).aspx

Checking the first key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Updates\UpdateExeVolatile

… showed that there were no entries.  However, checking the second key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\PendingFileRenameOperations

… showed the following:

\??\C:\Windows\System32\spool\PRTPROCs\x64\1_x5…

I looked at this key and thought: “HUH?”

Going with the hunch that this was probably a key left over from some other previous install, I renamed the key to:

_PendingFileRenameOperations

… then reran the Exchange Server 2010 language pack install and it completed successfully.  Definitely a strange issue.