I can't use files that I unzip

When you zip a binary file (this includes just about anything, including Microsoft Word, PageMaker, etc.) that is intended to go to a non-Macintosh, you should make sure that the MB and the LF indicators are both OFF (hollow) for each file in the archive. In Zipit 1.4 and earlier, the MB indicator is a circle in the MB column, and the LF indicator is a square. In ZipIt 2.0, the MB indicator has been renamed "Mac-only" and the LF indicator has been renamed "Text file". Both are checkboxes.

If either of these indicators is filled, then click on it to switch its setting. (The MB setting means convert to MacBinary, and the LF setting means translate linefeeds; neither of these is appropriate for a binary file going from a Mac to a PC.)

If the same thing happens on your end - i.e., if someone sends you a zip archive and you are unable to use the contents after successfully unzipping it - then you should try switching the setting of the LF indicator before unzipping the file.