PeaZip is a free, open source file and archive manager.PeaZip is available as portable and installable software for 32 and 64 bit Windows (9x, 2000, XP, Vista).
FlexibilityPeaZip can deploy fast compression in ZIP format, or very efficient speed / high compression ratio tradeoff in 7Z, BZ or ARC formats, or even highest levels of compression using PAQ family algorithms.
For any use PeaZip will help you in finding the better tool, since in compression field it doesn't exists a single best tool for all, but rather exist many good tools each fitting at best specific user's needs.
CompatibilityPeaZip can handle many archive and compression formats both from Windows worlds, ranging from mainstream ZIP format to experimental ones like PAQ/LPAQ. It is a reliable solution for most of the archive types you may met.
PortabilityYou can use PeaZip on all Windows version with basically the same features and look and feel: you can rely on the same archive utility on multiple systems and desktop environments. PeaZip is also available as standalone application, so you can even bring it with you whith no need to install it.