Guid and NativeGuid throws a COMException

I'm trying to create new OU in the root of Active Directory, but it constantly throws an exception.Could there be because I'm tot an admin?

Link to screenshot:

public void CreateGroup()
            DirectoryEntry dir = new DirectoryEntry("LDAP://ENCOTEC");
            DirectorySearcher search = new DirectorySearcher(dir);
            search.Filter = "(OU=IT System)";
            SearchResult it = search.FindOne();
            if (it == null)
                DirectoryEntry newEntry = dir.Children.Add("OU=IT System", "organizationalUnit");