http://www.rarlab.com/download.htm
Choose "Chinese Traditional" from "Localized WinRAR versions". A popup will appear and click execute. Follow the installation process. After the installation complete, you can open your rar file and you shall see on the top there is an icon called "Extract the files". You can then save the files inside the rar file as decompressed files.
2008-02-21 17:40:21 補充:
you may look at the pics provided by the yee2812 gei screen caps. we are mentioning the same software. It should be "Extract to" rather than "Extract the files". the software is very safe. no need to worry. it is the offical site to create and extract rar files.