after upgrading single to multi web site wordpress

After upgrading single to multi web site wordpress, I am getting my website URL http://www.webhostingpeople.net/ is going to url http://www.webhostingpeople.net/wp-signup.php?new=webhostingpeople.net

After adding code line in wp-confg.php " define( 'NOBLOGREDIRECT', 'http://www.webhostingpeople.net/wp-signup.php?new=webhostingpeople.net' ); " website is load fine but after some time again URL going to other. Please guide me how can I fix it.