File Compression

Stuffit and WinZip are compression utilities.
Stuffit files will generally have extensions SIT, ZIP, SEA, or DMG.
WinZip files can be either ZIP or EXE. Windows versions XP or later have ZIP functionality built into the Windows Explorer.

Stuffit can handle WinZip files, but not the other way around it.

Download Stuffit:

OS9
OSX
Windows
Stuffit Website

Download WinZip:

WinZip Website