What is 7-Zip?
7-Zip is an industry leading file archiver with a high compression ratio that is 50% more efficient than standard ZIP format. Use 7-Zip to pack and unpack a comprehensive list of supported compression formats.

What is RAR?
RAR is a file format that supports data compression. It basically takes large files and compresses them in size for transport. You end up with files name *.rar that contain other files.

How to open RAR files
Download and install 7-Zip. You can then open and extract RAR files from the 7-ZIP interface.

Supported Features
Packing/unpacking: 7z, ZIP, GZIP, BZIP2 and TAR
Unpacking only: RAR, CAB, ISO, ARJ, LZH, CHM, MSI, and more
Self-extracting capability for 7z format
Powerful File Manager
Powerful command line version
Supports WinZip-compatible AES-256 encryption
Can unpack MSI and WIM
Localization for 40 languages

Requirements
Windows 98/Me/NT/2000/XP/2003 Server/Vista
Command line version of 7-Zip can be used in Linux via Wine

About 7-Zip
7-Zip is open source software and is made freely availble for personal use. Source code and license information for 7-Zip can be found here:

7-Zip Project Page

RARLabs