As mentioned above, you will first need "Stuffit Expander". But also to point out: Unless you have a way of converting Mac files to PC or (I believe) Poser Pro Pack to read Mac files, it won't do you much good. You can however read several common files that may be included in a "sit' archive. I.E. jpegs and other image files. But you should have "Stuffit Expander" in your arsonal of must have apps anyway. James