How do you unzip a file that does not end in .zip? I tried finding something under the 'open with' option, but wasn't sure where the default unzip application is.
If the only difference between your file and other zip files is the file ending, you can simply change it to
.zip. If it's an archive but it uses another format, you can install 7zip or WinRar for free and unpack it with one of those - they support a wide variety of archive formats, hopefully yours too.