You need to get a RAR file converter. For Windows, you can get a 40 day free trial from RAR Labs - See the Related Link below. You may also need a password - that would have to come from the person that supplied the original RAR file.
In this case to my mind one of the best determinations. But last time I could solve out my trouble with rar files with the aid of one tool. It might help in this problem as well.
WinMount can mount RAR files on a new drive, so that you can use files inside it directly. There is no extraction time before you use them, and you don't need disk space to hold these huge files....