[ecfisa]

Hola noobdelphi5.

Aplica estos cambios:

Código Delphi [-]
...
  TForm1 = class(TForm)
    ListBox1: TListBox;
    procedure FormCreate(Sender: TObject);
  private
    procedure SoltarFichero(var Msg: TMessage); message WM_DROPFILES;
  ...

implementation

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

procedure TForm1.SoltarFichero(var Msg: TMessage);
var
  i, tFiles: integer;
  fName: array [0..MAX_PATH] of Char;
begin
  tFiles:= DragQueryFile(Msg.WParam, $FFFFFFFF, fName, MAX_PATH) - 1;
  try
    for i:= 0 to tFiles do
    begin
      DragQueryFile(Msg.WParam, i, fName, MAX_PATH);
      ListBox1.Items.Add(fName)
    end;
  finally
    DragFinish(Msg.WParam);
  end;
end;
...

Saludos