Microsoft Lync Server 2010 Installation Failure: Error code -2068643839

I recently ran in to an installation issue deploying a Lync Standard Edition server.  The server failed to install SQL Express instance prerequisite with error code -2068643839.  After some research and various attempts to get SQL installed, I found that this particular error is a known issue for SQL 2008, whereby if the account used for installing SQL or in this instance SQL Express, is not granted the 'Debug Programs' user right, the installation will fail.

A default installation of Windows Server 2008 R2 will grant the builtin\Administrators local group the correct user right; however some busiensses security policy will necessitate the removal of this user right. 
The solution for this is to grant the installation account the user right, run the installation and then remove the user right again so as not to compromise security.  To grant the user right do the following:

• Launch the 'gpedit.msc' MMC snapin
• Navigate to Computer > Windows Settings > Security Settings > Local Policies > User Rights Assignment
• Find the 'Debug programs' user right
• View the properties of the setting
• Click the 'Add User or Group' button
• Add the user that you are running the installtion with
• Click 'OK' all the way out

If the setting is being managed by GPO, it may be necessary to add the user via GPO.
At this point there will be a half installed version of SQL Express on the server which needs to be removed. 

• Uninstall the SQL instance via programs and features

It may be possible to run the installation again; however my experience was that the installation failed a second time with the same error and so I manually installed the SQL instance using the command:

• SQLEXPR_x64.exe /ACTION=Install /FEATURES=SQLEngine,Tools /INSTANCENAME=RTC /TCPENABLED=1 /SQLSVCACCOUNT="NT AUTHORITY\NetworkService" /SQLSYSADMINACCOUNTS="Builtin\Administrators" /BROWSERSVCSTARTUPTYPE="Automatic" /AGTSVCACCOUNT="NT AUTHORITY\NetworkService" /SQLSVCSTARTUPTYPE=Automatic

Choose the approproate instance name depending on if this is the RTC or RTCLOCAL instance.


Once this is done and the SQL instance is correctly installed, the Lync deployment wizard can be re-run and Lync should install correctly.  The other benefit of manually installing SQL is that the binaries can be installed on to a custom partition should that be required.