This error occurs when attempting to use Delphi 3 Client/Server features from Delphi 3 Professional or Standard editions. This could happen if you compiled the demos using a compiler other than the one that comes with Delphi 3 C/S. Check that the Delphi 3 Professional was not installed previously without first being un-installed. To correct this situation, uninstall Delphi, double check for leftover Delphi files, and finally re-install Delphi 3.0 C/S.