The AdtServer service does not start after you upgrade the operating system to Windows Server 2008 R2

Problem:
After you upgrade the operating system from Windows Server 2003 to Windows Server 2008 R2, the Adtserver service does not start. Additionally, the following event is logged:

Event ID: 4672
AdtServer encountered the following problem during startup:
Task: Open Audit Database
Failure: An error occurred connecting to the database
Error: 0x00000002
Error Message:
The system cannot find the file specified. Error2: The system cannot find the file specified when we attempt to start the service manually.

Impact:
The service that performs the audit collection service (ACS) Server functions cannot start. This occurs for both Operations Manager SP1 and Operations Manager R2. During ACS startup, the location of the Open Database Connectivity (ODBC) driver that is used for the data source is queried to make sure that it matches the location that is used in setting up the data source name (DSN). In Windows Server 2008 R2, the registry parameter for the location of the database driver contains environment variables instead of the actual path. The DSN uses "C:\Windows\System32\Sqlsrv32.dll" and the SQL Server driver uses "%Windir%\System32\SQLSRV32.dll." When the Adtserver process compares these values on startup to make sure that they are the same, the Adtserver process finds them different. This occurs only during an operating system upgrade.

Workaround:
Make the following registry change:

Subkey: HKEY_LOCAL_MACHINE\SOFTWARE\ODBC\ODBCINST.INI\SQL Server
Entry: Driver
Original value: %Windir%\System32\Sqlsrv32.dll
New value: C:\Windows\System32\Sqlsrv32.dll

On an Operations Manager 2007 R2 Audit Collection Services (ACS) server, apply Cumulative Update 1 (KB 974144) for the ACS server role before upgrading the ACS server operating system to Windows Server 2008 R2. If the KB 974144 update has already been applied to the ACS server role, the operating system can be upgraded without reapplying the KB 974144 update.
On an Operations Manager 2007 SP1 Audit Collection Services (ACS) server, apply the SP1 update rollup (KB 971541) for the ACS server role before upgrading the ACS server operating system to Windows Server 2008 R2. If the KB 971541 update has already been applied to the ACS server role, the operating system can be upgraded without reapplying the KB 971541 update.

More Info:
http://support.microsoft.com/kb/974722
http://support.microsoft.com/kb/971541