Reset the form style, then reset the height of the form. Note: You will need to add a method to terminate the application, as there will no longer be title bar buttons or a system menu. Example:

procedure TForm .FormCreate(Sender: TObject);
begin
  SetWindowLong(Form .Handle,
                GWL_STYLE,
                GetWindowLong(Handle,GWL_STYLE) and not WS_CAPTION);
  Height := ClientHeight;
end;