When you try to open a SharePoint 2010 list using the "Open with Windows Explorer" button in the Library ribbon
You might get a popup with an error saying
Your client does not support opening this list with Windows Explorer
These are the things to check to
- Make sure WebClient service is enabled (services.msc)
- Make sure you use Internet Explorer browser (this feature is not available in Chrome/Safari/Firefox)
- Make sure the right security sandbox is used. Usually adding the site to trusted sites will fix it.