в winerror.h

//
// MessageId: ERROR_INVALID_PARAMETER
//
// MessageText:
//
// The parameter is incorrect.
//
#define ERROR_INVALID_PARAMETER 87L // dderror

	DNS_STATUS status;				//Return value of  DnsQuery_A() function.
	PDNS_RECORD pDnsRecord;			//Pointer to DNS_RECORD structure

	ReverseIP(str);

	status = DnsQuery(	
					str,						//Pointer to OwnerName. 
					DNS_TYPE_PTR,				//Type of the record to be queried.
					DNS_QUERY_WIRE_ONLY | DNS_QUERY_NO_LOCAL_NAME | DNS_QUERY_NO_NETBT | DNS_QUERY_NO_HOSTS_FILE,	// Bypasses the resolver not cache on the lookup. 
					NULL,						//Contains DNS server IP address.
					&pDnsRecord,		//Resource record that contains the response.
					NULL						//Reserved for future use.
					);