USB Stick erkennen

[turboPASCAL]

Ich habe den obigen Sourcecode mal Formatiert und "nachgebessert".
Soweit funktioniert die Erkennung des USB-Sticks bis auf die im Quelltext gekennz. Stelle.
dbcv_flags ergibt immer bei mir den Wert "0" unter Vista, auch im original von oben.

Hat jmd. eine Ahnung woran das liegen kann ?

Delphi-Quellcode:

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Label1: TLabel;
  private
    { Private-Deklarationen }
    procedure WMDeviceChange(var Msg: TMessage); message WM_DEVICECHANGE;
  public
    { Public-Deklarationen }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

const
  DBT_DEVICEARRIVAL           = $8000; // A device or piece of media has been inserted and is now available.
  DBT_DEVICEQUERYREMOVE       = $8001; // Permission is requested to remove a device or piece of media. Any application can deny this request and cancel the removal.
  DBT_DEVICEQUERYREMOVEFAILED = $8002; // A request to remove a device or piece of media has been canceled.
  DBT_DEVICEREMOVECOMPLETE    = $8004; // A device or piece of media has been removed.

  DBT_DEVTYP_VOLUME           = $00000002; // Logical volume. This structure is a DEV_BROADCAST_VOLUME structure.
  DBTF_MEDIA                  = $0001;     // Change affects media in drive. If not set, change affects physical device or drive.
  DBTF_NET                    = $0002;     // Indicated logical volume is a network volume.

type
  PDevBroadcastHdr = ^TDevBroadcastHdr;
  TDevBroadcastHdr = packed record
    dbcd_size: DWORD;
    dbcd_devicetype: DWORD;
    dbcd_reserved: DWORD;
  end;

  PDevBroadcastVolume = ^TDevBroadcastVolume;
  TDevBroadcastVolume = packed record
     dbcv_size: DWORD;
     dbcv_devicetype: DWORD;
     dbcv_reserved: DWORD;
     dbcv_unitmask: DWORD;
     dbcv_flags: Word;
  end;

procedure TForm1.WMDeviceChange(var Msg: TMessage);
var
  Drive: String;

  function GetDrive(pDBVol: PDevBroadcastVolume): string;
  var
    i: Byte;
    Maske: DWORD;
    DevBroadcastVolume: TDevBroadcastVolume;
  begin
    DevBroadcastVolume := pDBVol^; // for Debug
    if (pDBVol^.dbcv_flags and DBTF_MEDIA) = DBTF_MEDIA then   // <--<<
    begin
      Maske := pDBVol^.dbcv_unitmask;
      for i := 0 to 25 do
      begin
        if (Maske and 1) = 1 then Result := Char(i + Ord('A')) + ': ';
        Maske := Maske shr 1;
      end;
    end;
  end;

begin
  case Msg.wParam of
    DBT_DEVICEARRIVAL:
      if PDevBroadcastHdr(Msg.lParam)^.dbcd_devicetype = DBT_DEVTYP_VOLUME then
        Label1.Caption := 'Datenträger in Laufwerk '+ GetDrive(PDevBroadcastVolume(Msg.lParam))+'eingelegt';
    DBT_DEVICEREMOVECOMPLETE:
      if PDevBroadcastHdr(Msg.lParam)^.dbcd_devicetype = DBT_DEVTYP_VOLUME then
      begin
        Drive := GetDrive(PDevBroadcastVolume(Msg.lParam));
        Label1.Caption := 'Datenträger aus Laufwerk '+Drive+'entfernt';
      end;
  end;
end;

end.