File extensions under Microsoft Windows operating systems
Hidden file name extensions for known file types under Windows
There is a little complication that all current versions of Windows OS (Windows 7 included) do not show file name extensions by default in Windows Explorer file manager or system file open/save dialog boxes shared by many programs.
Clear Windows installation has this feature disabled and file extensions are hidden to user. Known file types to operating system are recognized by its file extension in the background and visually represented to user by various graphic icons together with base file name without extension. This is due to Microsoft's policy that this way is maybe better for less advanced users, but it is also potentially dangerous for this same kind of users due security reasons. Microsoft prefers simplicity against security, because some dangerous and harmful files can be hidden under wrong file type and users does not have fully under control what they opens. When showing file extensions is disabled users can run dangerous scripts or applications and harm their computer. This problem is still frequently discussed and we think that hiding file extensions by default is wrong decision, but situation is still the same (Windows 7 or Windows Vista included).
More advanced users of Windows who wanting to keep their files and data under control, turning off "Hide extensions for known file types" Windows Explorer feature and displaying file extensions immediately after clear Windows installation. They also know many common file extensions and what to do with this file types.
If you need help how to show file extensions at your computer look at next FAQ articles about showing file extensions at various Windows versions.