Greetings, Gimmy - 

I suggest you read the PB Help topic titled "MDIClient object".

If I may expand a little on what Roland has explained: If you edit source for the frame window (w_prog_frame_mdi) in your app, at the very top you will likely see these lines (or something close):

forward
global type w_prog_frame_mdi from window
end type
type mdi_1 from mdiclient within w_prog_frame_mdi
end type

When you have a window of type MDI! or MDIHelp!, you can see by the source code that PB automatically creates an object of type MDIClient inside of the MDI (frame) window and names this object mdi_1. The visible workspace you see within a frame window is actually the MDIClient object. The MDIClient object is where all sheet windows are displayed, move, resized, etc. ... not the frame window. The frame window normally contains one thing... the MDIClient object, mdi_1.

Normally, PB automatically resizes mdi_1 to respond to toolbar changes, resizing of the frame window, etc. This is the behavior you are undoubtedly familiar with.

If you place an object, like a picture control, in your frame window, PB no longer performs any automatic resizing of the MDIClient object...You have to take on that responsibility. This is what the Help topic refers to as a "Custom MDI window".

HTH, Regards - John