Some files on this website have been compressed as self-extracting zip files so that they can be downloaded more easily from the Internet. Some browsers are configured to automatically uncompact (or "unzip") compressed files. If yours is, each compressed file that you download should be automatically uncompacted.
If your browser is not configured to decode files, you'll need a decoding utility to uncompact them. You can obtain evaluation versions of WinZip or Stuffit Expander from their websites. Other compression software is also available.
Use your decoding utility to uncompact each compressed file that you download.