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;