not getting hard drive serial number

Question

i have tried using the code 

searcher = new ManagementObjectSearcher("SELECT * FROM Win32_PhysicalMedia");

int i = 0;

foreach (ManagementObject wmi_HD in searcher.Get())

{

// get the hard drive from collection

// using index

HardDrive hd = (HardDrive)hdCollection[i];

// get the hardware serial no.

if (wmi_HD["SerialNumber"] == null)

hd.SerialNo = "None";

else

hd.SerialNo = wmi_HD["SerialNumber"].ToString();

++i;

}

 

 but this is not working for windows 8 and higher versions..