Windows platform. I've run the early versions on a 486-33 with Win 98. Self-contained app, but it gets very messy if you run a NG900, 9-3, 9-5 all at the same time. The new WIS 3.0 for 9-5 and 9-3SS integrates and is much better, but the old WIS will try to overwrite it and vice-versa.