It's widely assumed that the ideas for both Apple's and Microsoft's GUI-based operating systems were heavily lifted from research done at Xerox's Palo Alto Research Center, or PARC. And this clip from 1972, showing off Xerox's Alto desktop computer, all but proves the company was years ahead of its time.
Connected to other desktop computers via an ethernet network, the Alto demonstrated the earliest prototypes of a mouse driven UI, email, and even laser printers that perfectly reproduced what was seen on screen. Had the company treated this research as more than just fanciful R&D, Xerox could have literally owned the PC industry, instead of letting Microsoft and Apple steal its thunder. In fact the only thing missing, much to the chagrin of the office drone in this video who keeps talking to his computer, was voice recognition. But that's still far from perfected even 40 years later. [Crackajack via The Verge]