有沒有什麼software(要free)可以開rar檔案?

Try Win Zip, which is free and could open rar file.

你就free
唔識唔好亂答

http://www.7-zip.org/
７－ｚｉｐ　呢個唔駛錢又幾好用

winzip and winrar are both free softwares. you don't need to download them from official websites. there are tons of websites offer these two softwares for FREEEEEE!