In a blow to longtime leader Apple Computer Inc, Gateway Inc displaced it as the leader of loyalty among customers, according to a newly-released study from Ziff-Davis Corp. The loyalty findings measure the percentage of users who acquired a PC in 1997 that bought the same brand as the PC they had been using. For the first time, Gateway was the top brand, after being the number one or number two Wintel brand in each of the last three years. This year, a large decline by Apple propelled Gateway to the top of the ranking, with a 75% share. Hewlett-Packard Co came in second with 72%, while Apple slipped to third with a 71% rating.