Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine the core version of the Microsoft Windows® operating system running on each node in the cluster:

HKEY_LOCAL_MACHINE\Cluster\Nodes\ <Node Number> \BuildNumber

If the Exchange Server Analyzer finds the value for BuildNumber on the second or subsequent node in the Exchange cluster different from the value for BuildNumber on the first node in the Exchange cluster, an error is displayed.

If an Exchange cluster is running across disparate versions of Windows, failover may not occur as expected or configured. In a mixed vintage Windows environment, failover will only occur from an earlier operating system to a later operating system (for example, from Windows 2000 Advanced Server to Windows Server™ 2003, Enterprise Edition). It will not occur from a later operating system to an earlier operating system (for example, from Windows Server 2003 to Windows 2000 Server).

To resolve this problem, you must upgrade all nodes to the same operating system and service pack. To minimize downtime, you can perform a rolling upgrade of your cluster.

To correct this error

  1. Review the instructions for performing a rolling upgrade of a cluster, by reading the Microsoft Knowledge Base article 811272, "How to Perform a Rolling Upgrade of Windows Server 2003 Server Clusters" (

  2. Review the article, "Windows 2000 Clustering: Performing a rolling upgrade" (

  3. Perform a rolling upgrade of each node whose BuildNumber value is not the same as the first node in the cluster.

For information about alternative procedures, see "Alternatives to Rolling Upgrades" (