Windows 2003 SP2 compatibility issue with Exchange 2003 cluster

So you went ahead and installed Windows Server 2003 Service Pack 2 on your Exchange 2003 cluster because it’s a “good thing” (Not that service packs are not good things, they really are!).

Everything went well until all of a sudden, your users report that they can’t access their mailboxes through OWA. They complain that they get the dreaded “500 – Internal Server Error” message in their browsers.

Its time to dig into the Microsoft Knowledge base. KB article 841560 suggests that you install Exchange Server 2003 Service Pack 1 on your cluster and install hotfix 841561.

And then… you should find your problems melting away.