Get Hard disk serial Number

Hm, looking at your first set of code, I think you have retrieved (maybe?) the hard drive model. The serial # comes from Win32_PhysicalMedia.

Get Hard Drive model

    ManagementObjectSearcher searcher = new
    ManagementObjectSearcher("SELECT * FROM Win32_DiskDrive");

   foreach(ManagementObject wmi_HD in searcher.Get())
   {
    HardDrive hd = new HardDrive();
    hd.Model = wmi_HD["Model"].ToString();
    hd.Type  = wmi_HD["InterfaceType"].ToString(); 
    hdCollection.Add(hd);
   }

Get the Serial Number

 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;
   }

Source

Hope this helps :)

I have used the following method in a project and it's working successfully.

private string identifier(string wmiClass, string wmiProperty)
//Return a hardware identifier
{
    string result = "";
    System.Management.ManagementClass mc = new System.Management.ManagementClass(wmiClass);
    System.Management.ManagementObjectCollection moc = mc.GetInstances();
    foreach (System.Management.ManagementObject mo in moc)
    {
        //Only get the first one
        if (result == "")
        {
            try
            {
                result = mo[wmiProperty].ToString();
                break;
            }
            catch
            {
            }
        }
    }
    return result;
}

you can call the above method as mentioned below,

string modelNo = identifier("Win32_DiskDrive", "Model");
string manufatureID = identifier("Win32_DiskDrive", "Manufacturer");
string signature = identifier("Win32_DiskDrive", "Signature");
string totalHeads = identifier("Win32_DiskDrive", "TotalHeads");

If you need a unique identifier, use a combination of these IDs.

There is a simple way for @Sprunth's answer.

private void GetAllDiskDrives()
    {
        var searcher = new ManagementObjectSearcher("SELECT * FROM Win32_DiskDrive");

        foreach (ManagementObject wmi_HD in searcher.Get())
        {
            HardDrive hd = new HardDrive();
            hd.Model = wmi_HD["Model"].ToString();
            hd.InterfaceType = wmi_HD["InterfaceType"].ToString();
            hd.Caption = wmi_HD["Caption"].ToString();

            hd.SerialNo =wmi_HD.GetPropertyValue("SerialNumber").ToString();//get the serailNumber of diskdrive

            hdCollection.Add(hd);
        }

 }


public class HardDrive
{
    public string Model { get; set; }
    public string InterfaceType { get; set; }
    public string Caption { get; set; }
    public string SerialNo { get; set; }
}

Use "vol" shell command and parse serial from it's output, like this. Works at least in Win7

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace CheckHD
{
        class HDSerial
        {
            const string MY_SERIAL = "F845-BB23";
            public static bool CheckSerial()
            {
                string res = ExecuteCommandSync("vol");
                const string search = "Number is";
                int startI = res.IndexOf(search, StringComparison.InvariantCultureIgnoreCase);

                if (startI > 0)
                {
                    string currentDiskID = res.Substring(startI + search.Length).Trim();
                    if (currentDiskID.Equals(MY_SERIAL))
                        return true;
                }
                return false;
            }

            public static string ExecuteCommandSync(object command)
            {
                try
                {
                    // create the ProcessStartInfo using "cmd" as the program to be run,
                    // and "/c " as the parameters.
                    // Incidentally, /c tells cmd that we want it to execute the command that follows,
                    // and then exit.
                    System.Diagnostics.ProcessStartInfo procStartInfo =
                        new System.Diagnostics.ProcessStartInfo("cmd", "/c " + command);

                    // The following commands are needed to redirect the standard output.
                    // This means that it will be redirected to the Process.StandardOutput StreamReader.
                    procStartInfo.RedirectStandardOutput = true;
                    procStartInfo.UseShellExecute = false;
                    // Do not create the black window.
                    procStartInfo.CreateNoWindow = true;
                    // Now we create a process, assign its ProcessStartInfo and start it
                    System.Diagnostics.Process proc = new System.Diagnostics.Process();
                    proc.StartInfo = procStartInfo;
                    proc.Start();
                    // Get the output into a string
                    string result = proc.StandardOutput.ReadToEnd();
                    // Display the command output.
                    return result;
                }
                catch (Exception)
                {
                    // Log the exception
                    return null;
                }
            }
        }
    }