Delphi call winpcap and detect network adapter

Hello everyone:

I used Delphi codes  to cal winpcap to detect network adapter:

******************************************************************************************
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
        pDevice: PChar;
    errBuffArray: Array[0..1000] of PAnsiChar;
  public
    { Public declarations }
  end;


var
  Form1: TForm1;

  function pcap_lookupdev(errBuff: Array of PAnsiChar): PChar; cdecl; external 'wpcap.dll';

implementation

{$R *.dfm}

 
procedure TForm1.Button1Click(Sender: TObject);
begin
  pDevice := pcap_lookupdev(errBuffArray);
  ShowMessage('device: ' + pDevice);
end;

end.

*****************************************************************

but output result  always display 'device:\' rather than display the device name.

and if I call  

pcap_loop
pcap_open_live
pcap_findalldevs

..etc

I still can get the device id/name on xp

but it does not work on vista.

Welcome any comment.

Best Regards

Z Wang