I’m not really sure why the un-archive RAR utility is not come by default in windows since it can open various compress file format.
How to open a RAR file?
If you receive or download a *.rar file and unable to open it, you probably have heard of using the WinRAR to open it. However the problem is this WinRAR is evaluation copy! If you’re okay with evaluation copy - trial version, you can go ahead to download WinRAR software here.
To completely open the RAR with a free tool, you should try 7-Zip open source software.
Since 7-Zip this is the open source, don’t expect it is 100% free of bugs. I have been using it and I noticed there are few bugs here and there (e.g. browse button doesn't work). These bugs are usually minor and can be worked around pretty fast. Enjoy!
Download 7-Zip here.