Also, are you using a newer version of Aladdin Expander? I don't know about PC, but on Macintosh, you need to have both the freeware Expander and the shareware program Dropstuff to get Zip files to open. Dropstuff can be downloaded and tried out for free at www.aladdinsys.com. (I think the registration fee is $30 if you decide to keep it)