Patricia, I think UF will run on an Windows emulator on a Mac. Don't quote me on that, but I think I saw something about it when I was on the UF mailing list. I also saw that because of the chip intensive math computations running in a non-native environment, that it runs extremely slowly. Go here to subscribe to the mailing list to ask: http://www.ultrafractal.com/ or there is a link to the authors mail, Frederik Slijkerman, and he may be able to answer directly.