Here is the tool's "official" site: hxxp://d0wnl0ad.epicm.org/emrjt/index.html (zer0 for o letter)
This tool is not obligatory (just checked with Virustotal, 2/46, I presume some heuristics: hxxp://goo.gl/38qaJp ), it just is convenient as it automatically archives files if needed... There are also simple-as-nails .bat files doing the same for example:
@echo off
if /I %~x1==%~x2 exit
if /I %~x1 NEQ .jpg (if /I %~x2 NEQ .jpg exit)
if /I %~x1 NEQ .rar (if /I %~x2 NEQ .rar exit)
if /I %~x1==.jpg (
copy /b %1+ %2 "%~d1%~p1[rarjpg]%~n1.rar.jpg"
) else (
copy /b %2+%1 "%~d2%~p2[rarjpg]%~n2.rar.jpg")
Save this in a .bat file and drag (simultaneously selected) .jpg and .rar files to it, it will produce a PictureName.rar.jpg file :)
So there are plenty of ways, some utilities can even encrypt data and pack any file inside, not just RAR, but the resulting file cannot be opened with WinRAR :D