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//...
  if hnd <> INVALID_HANDLE_VALUE then
  begin
    ZeroMemory(@cmdIn, SizeOf(cmdIn));
    with cmdIn.irDriveRegs do
    begin
      bFeaturesReg := ENABLE_SMART;
      bSectorCountReg := 1;
      bSectorNumberReg := 1;
      bCylLowReg := SMART_CYL_LOW;
      bCylHighReg := SMART_CYL_HI;
      bDriveHeadReg := DRIVE_HEAD_REG;
      bCommandReg := SMART_CMD;

      ZeroMemory(@cmdOut, SizeOf(cmdOut));
      result := DeviceIoControl(hnd, SMART_SEND_DRIVE_COMMAND,
                                @cmdIn, SizeOf(cmdIn), @cmdOut, SizeOf(cmdOut),
                                bytesReturned, nil);
    end;
  end;
//...					

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  _SENDCMDOUTPARAMS = record
    cBufferSize: DWord;
    DriverStatus: TDriverStatus;
    bBuffer: array[0..0] of Byte;
    irDriveRegs: TIdeRegs;
  end;					

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const
  SMART_SEND_DRIVE_COMMAND     = $0007C084;
  ENABLE_SMART                 = $000000D8;
  SMART_CYL_LOW                = $0000004F;
  SMART_CYL_HI                 = $000000C2;
  SMART_CMD                    = $000000B0;
  DRIVE_HEAD_REG               = $000000A0;
  READ_ATTRIBUTES              = $D0;
  READ_THRESHOLDS              = $D1;

function SmartExists(ADriveLetter: Char): Boolean;
var
  root: PChar;
  hnd: THandle;
  cmdIn: TSendCmdInParams;
  cmdOut: TSendCmdOutParams;
  bytesReturned: DWord;
begin
  result := false;
  root := PChar('\\.\' + UpCase(ADriveLetter) + ':');
  hnd := CreateFile(root, GENERIC_READ or GENERIC_WRITE,
                    FILE_SHARE_READ or FILE_SHARE_WRITE, nil,
                    OPEN_EXISTING, FILE_ATTRIBUTE_SYSTEM, 0);

  if hnd <> INVALID_HANDLE_VALUE then
  begin
    ZeroMemory(@cmdIn, SizeOf(cmdIn));
    cmdIn.cBufferSize := 512;
    with cmdIn.irDriveRegs do
    begin
      bFeaturesReg := READ_ATTRIBUTES;
      bCommandReg := SMART_CMD;
      bDriveHeadReg := DRIVE_HEAD_REG;

      ZeroMemory(@cmdOut, SizeOf(cmdOut));
      result := DeviceIoControl(hnd, SMART_RCV_DRIVE_DATA,
                                @cmdIn, SizeOf(cmdIn), @cmdOut, SizeOf(cmdOut),
                                bytesReturned, nil);
    end;
  end;
end;