A quick Favorite Search Engine query consisting of "rar" will net you a myriad of results dealing with either programs that can extract rar-compressed archives or sites explaining where to find such programs. I find it difficult to comprehend how people these days are too lazy to go to their Favorite Search Engine and type three letters and find their answer.
Long story short, get Winrar (or 7-Zip, which I use). Also, locked.