Windows 7: help with compressing files

Can anyone provide me with a link to or a step by step tutorial on how to compress 6GB to max 4GB?
I've seen it been done with pc game files: you download a 3GB .rar file and unpack it to become a 6GB size folder. I want learn how to do this so that I can back my pc games.

Thanx ahead, guys. Looking forward to your replies and solutions



P.s. I realize that winrar isn't the only compression software, so if you could recommend me a software which can allow me to compress game files to fit on a dvd disc.

I really don't think there is a need to start another thread about this.
help with compressing files