The website
is a great website for know about programs related to any file extentions. If you get a file which does not open in any program you can find it here. Use the search box to enter any extension and the site will list any programs related to the extension
The website also has indexed entries from A-Z to browse the list of extensions. It also has downloads to automatically direct to the website through windows when you open a unkown extension
Michal
Hi, I think very useful file extensions searcher is File-extensions.org too:)) Michal