I downloaded my program to unzip rar files from Skeldale House and I love it. It's all I use now. If you download 50 files you can unzip all 50 at one time, not one at a time. You can also open it up and pic out only the format that you need. I also zip files to e-mail with it.
http://www.rarlab.com/ this should open the rar file; let us know how it works it will unzip the design as far as I know.
I was directed to this free download a couple years ago and I have used it to unzip RAR files...