Problem with IDesigner


I'm having problems with the following code line as I'm trying out the
latest Delphi (2007).

IFormDesigner = interface(IDesigner)

[DCC Error] DsgnIntf.pas E2003 Undeclared identifier: 'IDesigner'

The compiler can't find IDesigner. But wehn I look up IDesigner in the help
file the Interface class is sure there. But the file where it is inluded is
not there. Can this have some thing to do with the fact that I'm using a
trial version of Delphi? The code lines is within a third part component
that I bought and that costs at least a thousand of dollars to update.