Crystal Reports Server XI Upgrade to Crystal Reports Server 2008

The documentation for upgrading from Crystal Reports Server XI to Crystal Reports Server 2008 states that "If the installer detects that you already have a version of Crystal Reports Server XI or XI Release 2 on the computer that you are installing Crystal Reports Server 2008 on, the Crystal Reports Upgrade screen appears". This is designed to allow you to perform "simple upgrade".

WHen I try to run the install on the server with the simple installation of the Crystal Reports Server XI, I never get this message. Any reasons that this could happen?