I have industrial machines that run the user interface on Windows 3.1.<p>There was a fad for a while of not using PLCs, and instead using 'regular computers', at least for a portion of the system (usually a PLC still handled the most performance sensitive parts).<p>When you have a production line that's 100 feet of steel, motors, ovens, and other equipment, and the cost of redoing all the control systems is quoted at hundreds of thousands of dollars, then why change it? It still works.