One of the truisms about computers is that they're difficult. Despite the fact that the PC Revolution is now well into its third decade and the continuing improvements in the user friendliness of PCs and Macs, printers and scanners, and software and the Internet, using a personal computer can still be a hair-raising experience. This is particularly true with people older than 40 who weren't weaned on computers as kids are today. But it can be true with anybody who's not detail- or technically oriented, including people in work situations who need to use computers as part of their jobs. As many as two-thirds of managers/executives as well as clerical/support staff still feel hesitant about using technology in the office, according to research by Dr. Larry D. Rosen, psychology professor at California State University-Dominguez Hills, and Dr. Michelle M. Weil, president of the consulting company Human-Ware in Carlsbad, Calif.