How can I locate MAC file wwhen I am downloading a "Program." Everything I have seen has been for a IBM platform.. I.e. exe or zip

I sucessfully downloaded a zip file today that took about 4 hours and aver 100MB in size. When I opened the folder, all I had was a few PDF's and absolutely nothing to work with.

Please, share with me, as to how I can find a MAC download. http://www.gnutellaforums.com/confused.gif