You're trying to open CWZ files files you've received through an email attachment or a file on your hard drive, but your computer won't let you do it. You get an annoying pop-up window that says, "Windows can't open this file". What is a CWZ files file and how to open CWZ files? https://www.filemagic.com/en/data-files/cwz-file-extension/cwz-file-problems-why-your-pc-won-t-open-cwz-files/