Вы должны добавить нужные привилегии
ConnectionOptions connOptions = new ConnectionOptions();
connOptions.Impersonation = ImpersonationLevel.Impersonate;
//Add AuthenticationLevel that suits your need
connOptions.Authentication = AuthenticationLevel.PacketPrivacy;
connOptions.EnablePrivileges = true;
ManagementScope scope =
new ManagementScope("MANAGEMNET_PATH"
, connOptions);
scope.Connect();
ObjectQuery query = new ObjectQuery(
"YOUR QUERY");
ManagementObjectSearcher searcher =
new ManagementObjectSearcher(scope, query);