DD & form resizing

My game starts up in a form, then when you click on the start button it goes to DD and fullscreen mode. The problem occurs after I cleanup DD and go back to the form. The form's size is 640x480. What I changed the screen display to in DD. So I made two variables
FORM_WIDTH = frmMain->Width;
FORM_HEIGHT = frmMain->Height;

Then later reversed that to get the form's size right

After I did that the form's width would be right, but the height would still be 480, even though FORM_HEIGHT is like 230 or so. SO does anybody know why the program won't set a different height after Direct Draw.

Thanks