Windows Will Not Recognize a File Extension

Windows controls which programs open which files.

The Windows operating system is able to open files in their correct application when the user double-clicks on that file in a directory listing. This is because of a system in Windows called Default Programs. If Windows doesn't recognize a file extension, it is because there is something missing in the Default Programs settings.

Missing Application

A user may acquire a file on a setup disk, via Internet download, as an email attachment or from a CD or memory stick. Just because a file is on a computer does not mean the computer can handle the file type. The Windows operating system is unable to open many file extensions because certain files are only meaningful to certain applications. The software house that wrote the application invented the file extensions of the program's components and also the application's output files. Windows will not know how to handle a file extension and its operating applications unless this information is made available to the computer system.

Well-Known Extensions

A number of file extensions are already known to the Windows operating system, and the association with an application is already set when the Windows operating system is installed. An example of this is the extension EXE. Windows knows this is a program that it should run. Another file type Windows always knows how to handle is TXT, which is a file that opens in Notepad.

Default Programs

Access to the Default Programs system varies from version to version; however, it is available from the Control Panel of Windows. Most applications populate this database automatically when they are installed. The installer will associate the application with all of the file extensions it can handle. If an application installer does not perform this task, the user has to create the association manually.

Problem

A problem with the system is that it can associate many different file extensions with each application, but it can only associate one application with each file extension. A number of applications may use the same file extension, although the files they produce with that file extension do not have the same format. This means that an application will be registered to open all files with a particular file extension, but it will not be able to open a file that was created by a different application that happens to use the same file extension. There is no solution to this problem.

References

• Microsoft Windows: Change Which Programs Windows Uses by Default
• Windows 7 Library: Filename Extensions – Can’t Open .exe Files?
• Help Bytes: File Extensions and Their Role in Security