Windows Vista: The Complete Reference (Complete Reference Series)

In Windows, every file has a file type , determined by the file extension (usually three letters ) after the dot (see "What Are Extensions and File Types?" in Chapter 8). For example, My Proposal.doc has type DOC, so one usually calls it a DOC file. Every file type can be associated with a program or group of programs, so when you open a file of that type in an Explorer window (by clicking or double-clicking the file), the associated program runs automatically to process the file. Most programs associate themselves with the appropriate file types when you install the program, but in two circumstances, you may want to set your own associations:

• Dueling programs When two or more programs can handle the same type of file, whichever one you installed most recently wins, unless you intervene. This problem is particularly common with graphics formats such as GIF and JPG, because both graphics editing programs (such as the Windows Photo Gallery that comes with Windows Vista) and web browsers (such as Internet Explorer) can display them. You can change the association to whichever program you prefer, and Windows Vista can display a list of the programs that should be able to open a file.

• Nonstandard file extensions Many files with unknown types are, in fact, known types in disguise, or close enough to known types that a program you have installed can handle them. For example, most LOG files are actually text files that Notepad, WordPad, or any other text editor can read. Word processors can almost all read each other's files; for example, if you use WordPerfect rather than Word, you can associate DOC files with WordPerfect.

The Windows file association facility is complex and flexible. A file type can have several programs associated with it to do different actions, such as viewing and editing a file.

To see or change the details of a file association or to create a new association, open the Default Programs tool by choosing Start Default Programs. Choose Associate A File Type Or Protocol With A Program. Highlight an extension and click Change Program to choose a different program to run when you open that type of file. Windows lists the programs that it recommends for handling this type of file, along with other programs that it knows can open them. You can also browse to other programs that are not listed. (See "Associating Files with Programs by Using the Default Programs Option" in Chapter 3.)