When a form is called via DO FORM XXX.SCX is the current form not closed automatically???

I have a situation in which one form that is set to 800x600 but displayed on a 1024x768 screen fills all 1024x768 with the background picture (which is desirable). After a user presses a button, another 800x600 form is displayed on the 1024x768 screen is called but the new form does not fill all 1024x768. Instead, the 'calling' form's background stays in the 'unused' portion of the screen and as as such a user could click on that previous forms background and move it to the top.

I always thought that DO FORM XXX.SCX closed the current form. Is this not the case???

Also, I can not figure out why some of my forms sometimes have their background display tiled all the way out to the 1024x768 (as I wish) and others fill only the 800x600 and leave the balance as white (with the exception of the above noted form in which I am realy grasping at staws).

Ideas???