WinZip® 9.0 supports the Zip 2.0 standard file format, which is the specification used by the vast majority of applications on the market that process Zip files. The file with which you are working is not based on the Zip 2.0 standard and is not supported by this version of WinZip.
In order to work with this file using this version of WinZip, it will need to be re-zipped using a Zip 2.0-compatible program (such as WinZip itself).
For current information about file format compatibility, visit our web site at http://www.winzip.com/zip2.htm.