public static string GetDiskSerialNumber()
       {
           String HDid = "";           ManagementClass cimobject = new ManagementClass("Win32_DiskDrive");
           ManagementObjectCollection moc = cimobject.GetInstances();           foreach (ManagementObject mo in moc)
           {
               HDid = (string)mo.Properties["Model"].Value;
               if (HDid != "")
                   break;
           }
           return HDid;
       }