Hard Drive Real Serial Number

[hackerspk]

  Dim searcher As ManagementObjectSearcher = New ManagementObjectSearcher("SELECT * FROM Win32_PhysicalMedia")
        For Each wmi_HD As ManagementObject In searcher.Get()
            MessageBox.Show(wmi_HD("SerialNumber"))
        Next 

iam using this code for getting hard drive serial number its works ok with me but not working on my friends system and return an empty string any help plz