Free use zip software for windows

Are you using or thinking of Using Windows SharePoint Services 3.0 (WSS) or Microsoft Office SharePoint Server 2007 (MOSS) to allow users to upload and download files from a web-based environment? Excellent! SharePoint has a lot to offer you.
Background
SharePoint provides a great web-based user interface that allows a user to easily upload or download files, as long as the user is working with one file at a time. It would be really nice if users could download an entire set of files in one shot, or upload a set of files.
The Problem
There are approaches out there, but most require installing a client-side application like SharePoint Designer 2007 or using the SharePoint file upload ActiveX control, which does not allow uploading files from multiple folders at once. While these approaches may be OK for intranet portals is not ideal for extranet or Internet SharePoint deployments.
A Simple Solution
Use Zip files. Zip files allow users to package multiple files and folders into a single file and then unpack the contents later. Most desktop and laptop computers are able to work with Zip files. SharePoint Zip allows users to upload a single Zip file into a SharePoint document library, and tell SharePoint to unzip the contents of the file after the upload has completed.
This not only makes the upload simple, only one file is sent to SharePoint, but also the contents of the Zip file are compressed, saving valuable upload time and bandwidth. Downloading is just as easy. Users select a file, folder, or entire document library, and SharePoint sends the contents as a single Zip file. This saves considerable time and bandwidth during the download, and it lets users download many files and folders with a single click.
SharePoint Zip was designed to let you transfer many files between SharePoint and your desktop as a single package.

System requirements:
- Windows SharePoint Services 3.0 (WSS) or Microsoft Office SharePoint Server 2007 (MOSS)

Enhancements:
- SharePoint Zip 2.0 now supports forms-based authentication. This makes SharePoint Zip a great tool for intranet, extranet, and now Internet SharePoint sites!
- SharePoint Zip 2.0 now supports downloading and uploading of very large (multi-gigabyte) Zip files. This is a must-have for SharePoint sites that store large documents, like digital images and video files.
- SharePoint Zip 2.0 supports load-balanced SharePoint farms. The workload of processing Zip file contents now scales across all web front-end servers in the SharePoint farm.