Did you also use the ZIP drives compression features to further compress your already winzipped files?
Do you have winzip on your current system and have you tried using it to unzip the files since the self-extracting doesn't seem to be working.
You can also contact WinZip at this page: (
http://winzip.com/xtech.htm) and describe to their tech support your problem. In the past I have found their people bend over backwards to help.
Good luck