uses
  Graph, crt, dos;

var Gd, Gm : integer;

var Window : array [1 .. 11] of record
              x : integer;
              y : integer;
              x2 : integer;
              y2 : integer;
              P : pointer;
             end;

procedure DrawWindow (handle : integer);
          var x1, y1, x2, y2 : integer;
          var Size : integer;

          begin
          x1 := Window[handle].x;
          y1 := Window[handle].y;
          x2 := Window[handle].x2;
          y2 := Window[handle].y2;

          Size := ImageSize(x1,y1,x2,y2);
          GetMem(Window[handle].P, Size);
          GetImage(x1,y1,x2,y2,Window[handle].P^);

          {Commands to draw window
                .
                .
                .
                                }
        end;

begin

Gd := Detect; InitGraph(Gd, Gm, 'c:\tp\bgi');

Window[1].x := 20;
Window[1].y := 20;
Window[1].x2 := 400;
Window[1].y2 := 400;

DrawWindow (1);

readln;

end.

...1.) When lazy, forbid windows allocating more than 64k bytes.., ;-)) not
recom...

...2.) When good at maths (well uhm.. I am not... at least not that good...
;-))
You have to add MORE POINTERS to the WINDOW RECORD. (1st)
You have to CREATE a PROCEDURE that DEVIDES the WINDOW in several 64K-PARTS
using those pointers...(2nd)
The procedure that devided the window in parts must also remember, where
each part starts and stops (these are subwindows, in a way).(3rd)

Try it and OPTIMIZE it!

Hope it helps.. ;-.))