ZIP archives are compressed files that require an "unzipping" utility to open them. Windows XP has a built-in file decompression utility. For other operating systems, here are some suggestions:
For Windows Systems
- AlZip is a free, easy-to-use compression/decompression utility. It will run on Windows 98 or above. It appears to be a relatively new product, but I've tried it and it seems to work quite well.
- WinZip is the best known compression/decompression utility for Windows. It will run on Windows 98 or above and has lots of bells and whistles along with a proven track record. You can download a free trial, but it costs $29.95 for a registered version.
For Macintosh Systems
- Stuff-it Expander is the classic free decompression utlity for the Mac. The latest version runs only on OS X, but a version that runs on older operating systems is still available. The free version is for opening compressed files only. If you need to make compressed files, there are several versions you can purchase.