天道酬勤 获取硬盘序列号并加密

获取硬盘序列号的方法如下（但好像获取的是逻辑硬盘的，不知物理硬盘的如何获取？）： 

string disknumber = ""; 
    string mSQL = "SELECT *FROM Win32_DiskDrive"; 
    ManagementObjectSearcher mos = new ManagementObjectSearcher(mSQL); 
    ManagementObjectCollection moc = mos.Get(); 
    foreach(ManagementObject mobject in moc) 
    { 
     disknumber = mobject.Properties["PNPDeviceID"].Value.ToString().Trim(); 
    }

对获取的序列号加密的方法： 
   

str = System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(str ,"SHA1"); 
    str = str.GetHashCode().ToString().Trim(); 
    str = System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(str,"MD5");

另外，不知用API的方法如何获取？各位达人帮忙啊。