I’m trying to upgrade a SMS 2003 Secondary Site to ConfigMgr 2007 but the option to upgrade the Site is greyed out. I’m seeing this in the ConfigMgrSetup.log:
Setup has detected an existing installation of the administrator console. This server seems to be a site server for a secondary site. Because the current installation is a different version, you do not have the option of modifying the installation.
The reason for the error is Microsoft assumes that the SMS Admin Console is not installed on a Secondary as there’s no real point. Although you can do it, there’s very little point as you need to connect back to the Secondary’s Parent Primary Site in order to be able to administer the Secondary Site.
Uninstall the Administrator Console from the Secondary Site then re-attempt the upgrade to ConfigMgr at which point you will be able to upgrade it.