The Microsoft Corporation announced its first significant software acquisition in 1987, paying $14 million for Forethought Inc. of Sunnyvale, Calif. Forethought makes a program called Powerpoint that allows users of Apple Macintosh computers to make overhead transparencies or flip charts. Some industry officials think such desktop presentations have the potential to be as big a market as desktop publishing, which involves using computers to lay out newsletters and other publications. Microsoft is already the leading software supplier for the Macintosh.