Hi Steve,
Thanks for your reply! Yes, the ODBC driver is the AIM AT Historian x32 version, provided by Invensys. Actually the x32 ODBC setup is our last resort .. We've tried initially OLEDB but Invensys had problems setting it up for us on a Win 2008 Enterprise 32 bit system (they have their own compatibility lists too).
The second step was to build an Win 2008 R2 Enterprise (x64) machine where PCo runs now in 32 bit mode. With this setting and the AIM*AT Historian OLEDB provider installed, we can't see and select any AIM*AT Historian servers in the Data Link Properties tab in Source systems -> PCo OleDB Database connection - > Configuration settings.
The same AIM server seemed accessible via system ODBC, where testing the connectivity to Excel was working pretty well (you can't pool connections, though). Regarding OPC, (DA and/or HDA) there's no license in place for us, so we could not test anything in this regard.