I'm not entirely sure what happened, but I know that for me atleast the second I finished download unRAR from winrar my computer crashed and I had to revert it back to the way it was the day I bought making me have to reset pics, passwords, AV software, music, everything. Maybe it was a rare case, but I've decided I personally won't be having anything to do with anything involving RAR of any kind.
Sounds like you fail at Windows.
It sounds harsh, but I can't imagine what you did to get that to happen. Perhaps you downloaded winRAR from a fake site and it was actually something malicious. I guess I can imagine what you did after all!
Just download http://www.7-zip.org/. It opens just about any archive format you could encounter.
Furthermore, it's free and open source. Enjoy.