Whenever it is time to install a service pack every DBA silently hopes that nothing will go wrong. I would surmise that, in most cases, installing the service pack is a non-event. No flashing lights, no fireworks, no applause and no major hiccups. This post is not about one of those times.
The Install
Several weeks ago I attempted to install SQL Server 2008 R2 Service Pack 3 on one of our production instances. The server was already at SP2 so it was to be a routine install. However, as the installer launched, this error appeared: