Are you sure you have the correct version of winrar? I have downloaded it dozens of times for new build systems & never experienced the problem you describe. On the rarlabs website (which is where I hope you downloaded it from), there are several download options available depending on o/s version no. etc.
If you chose to download it from somewhere other than rarlabs.com, there is a possibility you have acquired added warez designed to relieve you of your cash. Once installed, the best way to use it is to right click on the target file & choose extract files... rather than open up winrar itself.