Add datawindow control for master datawindow

Hi,
I hope you dont't mind an newbie question here. I am following the
tutorial of the Getting Started PB5 manual and I am stuck in chapter 8
"Building Ancestor Windows". Here are the steps:
1. I create a new window ( a master/detail window)and want to add a
control to be the master DataWindow in the applic.
2. I select the UserObj button and choose TUTOR_PB.PBL
3. When I click OK the manual tells me to click in the upper left corner
but nothing happens: there is already a blanc window visible, which I
can't move with the mouse.
4. I select Properties. The name of the Properties dialog box is
"Datawindow", not "Datawindow inherited from u_dwstandard" as it should
be according to the manual.
Now I can't change the Name field "u_dwstandard" to "dw_master" for
instance.
In step 3 when I click "Inherit" instead of "OK" I get the same result.
If someone could point me in the right direction ?? Thanks very much.
Regards,
marc