private
  procedure WMDROPFILES(var Msg: TMessage); Message WM_DROPFILES;


procedure TForm1.WMDROPFILES(var Msg: TMessage);
var
 i, Counts, Size: Integer;
 PCharFileName: PChar;

begin
 inherited;
 PCharFileName:=nil;
 Counts:=DragQueryFile(Msg.WParam, $FFFFFFFF, PCharFileName, 255);
 for i:=0 to Counts - 1 do
  begin
   Size:=DragQueryFile(Msg.WParam, i, nil, 0) + 1;
   PCharFileName:=StrAlloc(Size);
   DragQueryFile(Msg.WParam, i, PCharFileName, Size);
   ListBox1.Items.Add(String(PCharFileName));
   StrDispose(PCharFileName);
  end;
 DragFinish(Msg.WParam);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
 DragAcceptFiles(ListBox1.Handle, True);
end;