AT the Cupertino office of the beleaguered US giant, Apple Computer Inc., a massive drive is on to eliminate the worm in its operations. For the second quarter of fiscal 1996, the company announced a $740 million loss and plans to shed over 1,500 jobs. Hounded by Wall Street and the financial media for its flagging performance, it has ousted chief executive Michael Spindler, narrowly survived a merger with Sun Microsystems, and brought in Gil Amelio to supervise the spring cleaning. The new CEO has overhauled the top management so fast that those who got up from their chairs, the story goes, found it reoccupied before they could ease themselves back.