[Alegun]

Сообщение от HTTqp

...после запуска программы, она начинает постоянно проверять...

Зачем постоянно-то, при удалении/появлении в усройстве нового сиди системой генерится сообщение WM_DEVICECHANGE, в этот момент и надо ловить, вот пара способов из drkb

Код:

{ 
Some applications need to know when the user inserts or 
removes a compact disc or DVD from a CD-ROM drive without 
polling for media changes. Windows provide a way to notify these 
applications through the WM_DEVICECHANGE message. 
}

type
  TForm1 = class(TForm)
  private
    procedure WMDeviceChange(var Msg: TMessage); message WM_DEVICECHANGE;
  public
  end;

{...}

implementation

{$R *.DFM}

procedure TForm1.WMDeviceChange(var Msg: TMessage);
const
 DBT_DEVICEARRIVAL = $8000; // system detected a new device 
 DBT_DEVICEREMOVECOMPLETE = $8004;  // device is gone 
var
  myMsg: string;
begin
  inherited;
  case Msg.wParam of
    DBT_DEVICEARRIVAL: myMsg  := 'CD inserted!';
    DBT_DEVICEREMOVECOMPLETE: myMsg := 'CD removed!';
  end;
  ShowMessage(myMsg);
end;

и

Код:

// Advanced Code: 
// When the device is of type volume, then we can get some device specific 
// information, namely specific information about a logical volume. 
// by Juergen Kantz 

unit Unit1;

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    label1: TLabel;
  private
    procedure WMDeviceChange(var Msg: TMessage); message WM_DeviceChange;
    { Private declarations }
  public
    { Public declarations }
  end;
const
  DBT_DeviceArrival = $8000;
  DBT_DeviceRemoveComplete = $8004;
  DBTF_Media = $0001;
  DBT_DevTyp_Volume = $0002;

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

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

var
  Form1: TForm1;
implementation

{$R *.dfm}

function GetDrive(pDBVol: PDevBroadcastVolume): string;
var
  i: Byte;
  Maske: DWORD;
begin
  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;

procedure TForm1.WMDeviceChange(var Msg: TMessage);
var
  Drive: string;
begin
  case Msg.wParam of
    DBT_DeviceArrival:
      if PDevBroadcastHdr(Msg.lParam)^.dbcd_devicetype = DBT_DevTyp_Volume then
      begin
        Drive := GetDrive(PDevBroadcastVolume(Msg.lParam));
        label1.Caption := 'CD inserted in Drive ' + Drive;
      end;
    DBT_DeviceRemoveComplete:
      if PDevBroadcastHdr(Msg.lParam)^.dbcd_devicetype = DBT_DevTyp_Volume then
      begin
        Drive := GetDrive(PDevBroadcastVolume(Msg.lParam));
        label1.Caption := 'CD removed from Drive ' + Drive;
      end;
  end;
end;
end.

это всё под CD-диск заточено, но думаю константы совпадают и для болванок