Looking for Hard Disk Serial Number

using System.Management;

public string GetHDDSerial()
{
    ManagementObjectSearcher searcher = new ManagementObjectSearcher("SELECT * FROM Win32_PhysicalMedia");

    foreach (ManagementObject wmi_HD in searcher.Get())
    {
        // get the hardware serial no.
        if (wmi_HD["SerialNumber"] != null)
            return wmi_HD["SerialNumber"].ToString();
    }

    return string.Empty;
}