Until recently, you could open all .exe files on your Mac with Stuffit Expander. Versions 10 and 11 cannot open them properly (Version 12 does open them properly). There is a way to open them, however, if you use OS X. (If you still have Expander version 9 or older, you should have no problems opening the .exe files).
This process uses the Terminal, which is part of the Unix operating system underneath OS X.
A small window should open. Verify you're at the computer's root. If the person who logged in has the computer nickname Jeff, "root" in the terminal should look like this...
~ jeff$

Type cd Desktop and press the Return key. The terminal should now look like this...
~ /desktop jeff$
This process will work for any of SiteSell's or Site Build It!'s .exe files.