Geo, you can continue using the free version for as long as you want, but as the others said, you have to pay for the Pro version which runs in real time. If you watch Newegg.com, they often have it on sale for $15. I always grab a couple of copies when they do as it is so good at stuff like Homer6 mentions. I said this in another thread, but it stopped something similar on my 89 year-old mother's computer. I live 600 miles away, so this really saved me!
Fireplace, yarn, knitting needles, books, wine... check. Yup, I'm ready for winter.