A ZIP file is a "compressed" format file. A ZIP file is much smaller than the size of the uncompressed file, greatly reducing the possibility that your email server will reject our email due to the size of the attachment. ZIP files can be managed with any one of a number of programs. Some are free to download. Many users will already have a utility included with the software on their pc.

Instructions for Windows XP (which comes with a built-in utility)

Instructions for Windows Vista (built-in utility)

Utilities for other versions of Windows OS (Freeware/Shareware)