You only need to download RAR for DOS to use RAR32.exe if you are going to run it in OS/2, or in the original MS DOS.

If you need to run RAR for DOS (RAR32.exe) in a Windows DOS box or as a command prompt, we strongly suggest you instead use RAR.exe from your /WinRAR folder. It is a command line tool and its command line syntax is practically the same as for the DOS version, but unlike RAR32.exe, RAR.exe is a native Windows application, so it is more reliable and efficient when used inside Windows. Also RAR.exe provides a number of very useful Windows specific options that are not available in the DOS version.