How to display message box when starting up an Inno Setup installer

Question

How to display a message box information, when starting up an installer made in Inno Setup?

Like this setup of Reloaded Games does:

Answer 1

Call the MsgBox function from the InitializeSetup event function:

function InitializeSetup(): Boolean;
begin
  MsgBox('Some message.', mbInformation, MB_OK);

  Result := True;
end;