There are free programs for opening .rar files. You can google for them.
However, the first thing I'd recommend to you is to get sufficient protection against any kind of virus, trojan, malware or whatever culprits there are because from my experience with program files downloaded from the network, you will have to deal with those nasties in 999/1000 cases:
So, here my links for you:
http://www.lavasoftusa.com/software/adaware/(free) Spybot - Search & Destroy (FREE) AVG - Free Antivirus Program 