Zip files are used because they take up less space to store, and take less time to send or download. They are also a very convenient way to package and send groups of related files. However, the files must be extracted or unzipped from the archive before they can be used.
Most modern operating systems on PCs will allow you to unzip files without having to download special programmes. These examples are screenshots from Windows 7.
From the catalogue page:
I clicked on the PDF icon, and this window opened.
I clicked on "open" and the following window appeared. I clicked on "Extract all files"
and chose to have the folder extracted to my Desktop. I could have chosen any other location using the "browse" button (not shown, but just to the right of this screenshot)
You can view videos about "unzipping" or "extracting"on You Tube. Try these.
http://youtu.be/0iHfXTfMenI (Windows 7, no audio)
http://youtu.be/e5gRPNOW9AY (Older, with full commentary, and a bit long:start at about 2'50" )