uses
 ShellAPI;
function MakeDrop(const FileNames: array of string): THandle;
// Creates a hDrop Object
var
 I, Size: Integer;
 Data: PDragInfoA;
 P: PChar;
begin
 // Calculate memory size needed
 Size := SizeOf(TDragInfoA) + 1;
 for I := 0 to High(FileNames) do
  Inc(Size, Length(FileNames[I]) + 1);
 // allocate the memory
 Result := GlobalAlloc(GHND or GMEM_SHARE, Size);
 if Result <> 0 then
 begin
  Data := GlobalLock(Result);
  if Data <> nil then
  try
  // fill up with data
  Data.uSize := SizeOf(TDragInfoA);
  P := PChar(@Data.grfKeyState) + 4;
  Data.lpFileList := P;
  // filenames at the at of the header (separated with #0)
  for I := 0 to High(FileNames) do
  begin
  Size := Length(FileNames[I]);
  Move(Pointer(FileNames[I])^, P^, Size);
  Inc(P, Size + 1);
  end;
  finally
  GlobalUnlock(Result);
  end
  else
  begin
  GlobalFree(Result);
  Result := 0;
  end;
 end;
end;
function MyEnum(Wnd: hWnd; Res: PInteger): Bool; stdcall;
// search for a edit control with classname 'TEditControl'
var
 N: string;
begin
 SetLength(N, MAX_PATH);
 SetLength(N, GetClassName(Wnd, Pointer(N), Length(N)));
 Result := AnsiCompareText('TEditControl', N) <> 0;
 if not Result then Res^ := Wnd;
end;
// Example: Open msdos.sys in Delphi's Editor window
procedure TForm1.Button1Click(Sender: TObject);
var
 Wnd: HWnd;
 Drop: hDrop;
begin
 // search for Delphi's Editor
 EnumChildWindows(FindWindow('TEditWindow', nil), @MyEnum, Integer(@Wnd));
 if IsWindow(Wnd) then
 begin
  // Delphi's Editor found. Open msdos.sys
  Drop := MakeDrop(['c:\msdos.sys']);
  if Drop <> 0 then PostMessage(Wnd, wm_DropFiles, Drop, 0);
  // Free the memory?
  GlobalFree(Drop);
 end;
end;