A .rar file is a compressed or sometimes called zipped file
info here:
http://www.tech-pro.net/howto_030b.html
winrar is a free to try extractor (I've had it for a while and it does ask you to register purchase etc in a pop up window after the evaluation, it still works if you do not register or purchase it)
http://www.winrar-downloads.com/
also just right clicking the file might bring up a built in windows extractor
port