I'd recommend 7zip it is more robust and generally better in every way. It's also free. 7-zip dot org
Key File for WinRar is here: http://www.box.com/s/eacb98d5f31755f5b8ba Code (markup): Just download and copy into your WinRar folder. Goodluck !
Do you really need Winrar, you can use some free alternative programs like B1 Free Archiver. It's much simpler in use than other archiver programs. What i'd like to mention either is that it has nice and informative manuals like this for opening .rar files: http://b1.org/help/How-to-open-rar-file-and-unrar-files-from-rar-archive-in-one-click.jsp