Lots of people on Planet minecraft have trouble downloading and unzipping RARs. This can be done with WINRAR, yet it costs money BUT, i have found a solution.

http://www.unrarx.com

What UNRARX can do is the same thing as WINRAR, yet free.

here are some steps on how to unzip RARs with UNRARX

Step 1. download UNRARX and wait until the download is ready

Step 2. find a RAR file you want to unzip and click on it

Step 3. once the UNRARX unzip window is open, click on where it says "file directory" then click on "desktop"

Step 4. Go to the top-right corner of the window and click on "extract"

Step 5. wait for UNRARX to unzip your RAR file, When its done, the new file should be right on your desktop!