Filenames, for files that have been compressed with UNIX compress or Gzip, should be in the format filename.ext.z or filename.ext.gz. When downloading files, some browsers will replace the first dot ( . ) in the filename with an underscore ( _ ). The browser may also change the file extension at the end of the filename (.gz or .z).
For example, if you are attempting to download a file which displays as filename.tar.gz on the server, it may download as filename_tar.gz or filename_tar.tar. You will need to rename the archive while downloading (or after the download completes), so that the name is in the correct format. Otherwise, when you try to open it with WinZip, the attempt will fail.
Opening UNIX compress files
When opening a .z or .gz archive with the WinZip user interface, you may not see the files at first. You will need to change the selection in the drop-down menu next to the File name box from Zip files to All archives. After doing this, .z and .gz files will display in the Open WinZip File dialog.
False .z files
A popular installation program creation tool (InstallShield) uses files with a filename extension of .z. In spite of this filename extension, however, these files are not in the Unix compress format; their format is proprietary and WinZip cannot extract from them.