type
  TForm1 = class(TForm)
  Button1: TButton;
  private
  { Private declarations }
  procedure WMDeviceChange(var Message: TMessage);
  message WM_DEVICECHANGE;
  public
  { Public declarations }
  end;
  var
  Form1: TForm1;
  implementation
  {$R *.DFM}
  const DBT_DEVICEARRIVAL = $8000;
  const DBT_DEVICEQUERYREMOVE = $8001;
  const DBT_DEVICEQUERYREMOVEFAILED = $8002;
  const DBT_DEVICEREMOVEPENDING = $8003;
  const DBT_DEVICEREMOVECOMPLETE = $8004;
  const DBT_DEVICETYPESPECIFIC = $8005;
  const DBT_CONFIGCHANGED = $0018;
  procedure TForm1.WMDeviceChange(var Message: TMessage);
  var
  s : string;
  begin
  {Do Something here}
  case Message.wParam of
  DBT_DEVICEARRIVAL :
  s := 'A device has been inserted and is now available';
  DBT_DEVICEQUERYREMOVE: begin
  s := 'Permission to remove a device is requested';
  ShowMessage(s);
  {True grants premission}
  Message.Result := integer(true);
  exit;
  end;
  DBT_DEVICEQUERYREMOVEFAILED :
  s := 'Request to remove a device has been canceled';
  DBT_DEVICEREMOVEPENDING :
  s := 'Device is about to be removed';
  DBT_DEVICEREMOVECOMPLETE :
  s := 'Device has been removed';
  DBT_DEVICETYPESPECIFIC :
  s := 'Device-specific event';
  DBT_CONFIGCHANGED :
  s:= 'Current configuration has changed'
  else s := 'Unknown Device Message';
  end;
  ShowMessage(s);
  inherited;
  end;