Artwork: Chip TaylorIBM’s first PC, announced on August 12, 1981, was far from the first personal computer–but when it arrived, there was near-universal agreement that it was likely to be a landmark machine. It was. And 25 years later, it still ranks among the most significant computers ever. Like the IBM Personal Computer, Model 5150, the greatest systems have always had ambitions to boldly go wh