"WinRAR is a powerful archive manager. It can backup your data and reduce size of email attachments, decompress RAR, ZIP and other files downloaded from Internet and create new archives in RAR and ZIP file format."
WinRAR is a 32-bit Windows version of RAR Archiver, an archiver and archive manager. RAR files can usually compress content by 8 percent to 15 percent more than ZIP files can. WinRAR's main features include strong general and multimedia compression, the ability to process non-RAR archive formats, ZIP compression and decompression, support for long filenames, programmable self-extracting archives (SFX), repair of damaged archives, authenticity verification, embedded file comments, and encryption. Unicode is supported in archive filenames, allowing non-English filenames to be handled painlessly. You can manipulate the parameters of many archives at once and view a volume sequence as a single archive. WinRAR can convert other archive formats to RAR and search for specified text and files in archives.
Major changes for version 3.70 includes: better Vista compatibility, fixes the stack overflow vulnerability, support for the UDF file format, unicode support for CD ISO images, longer filenames and a new command line option for self-extracting modules.
Source with Changelog: 9Down.com