Sure, I suppose 'CORP' is the logon domain name of useraccount 'dthielen'.
In this case you to connect to the domain controller and use the
Win32_UserAccount class and you have.
Win32_SystemAccount and Win32_UserAccount are subclasses of Win32_Account.
The former only contains the default local system accounts
(localaccount==true), the second represents the non local accounts
(localaccount == false).

Here's a sample:

public static void Main() {
 //Connect to the remote computer
 ConnectionOptions co = new ConnectionOptions();
 // specify credentials of a valid account with sufficient privileges to
query the root\cimv2 namespace
 co.Username = "administrator";
 co.Password = "somepasswd";
 // Connect to the DC using above credentials
 System.Management.ManagementScope ms = new
System.Management.ManagementScope(@"\\DCforCORP\root\cimv2", co);
 GetAccountSid("CORP", "administrator", ms);

}
static void  GetAccountSid(string domain, string name, ManagementScope ms )
{
 string accountSid;
 string CIMObject =
String.Format("win32_useraccount.domain='{0}',name='{1}'", domain, name);
 Console.WriteLine(CIMObject);
 using(ManagementObject mo = new ManagementObject(CIMObject))
 {
  mo.Scope=ms;
  mo.Get();
  accountSid = mo["SID"].ToString();
  Console.WriteLine(accountSid);
 }
}

Willy.