// ...
    UINT nDriveNumber = 0;
    CString strSerialNumber;
    DWORD dwResult = GetPhysicalDriveSerialNumber(nDriveNumber, strSerialNumber);
    CString strReport;
    if (NO_ERROR == dwResult)
    {
        strReport.Format(_T("Drive #%u serial number: '%s'"), nDriveNumber, strSerialNumber);
    }
    else
    {
        strReport.Format(_T("GetPhysicalDriveSerialNumber failed. Error: %u"), dwResult);
    }
    ::MessageBox(NULL, strReport, _T("Test"), MB_OK);