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Reassign File Associations in Windows

Windows remembers which programs are associated with each file type, so when you double-click on a file in Explorer, Windows knows which program to launch. For example, if the file ends in .XLS, typically Microsoft Excel will be launched.

However, some file types may be assigned to many programs, such as .MP3 and .JPG and so applying a Service Pack or installing a new program may reassign the file associations, either back to the system defaults or away from the system defaults.

If you find that the a file is no longer being opened by the program of your choosing, the association can be restored easily:

  1. Open Windows Explorer using Start, Programs, Accessories, Windows Explorer.

    Tip: You can also right-click My Computer and click Explore.

    Tip: You can also press Windows Key - E (ÿ-E) on your keyboard.

  2. Find an instance of the file type in question (it does not matter which file).

  3. Right-click the file. The file type's context menu will appear. Depending on the existing associations, you will see one of three things: (1) an option called Open With, (2) a sub-menu called Open With showing multiple existing associations, or (3) no mention of Open With (in which case the association cannot be changed).

  4. Click Open With... or use the sub-menu to click Choose Program (as the case may be):

  5. Choose the appropriate program, ensure Always use the selected program to open this kind of file is enabled and click OK.

    If the program required does not appear in the list, click Browse to find the program on your hard disk.

Assigning File Types for Older Applications

Either by design or bug, some versions of Windows disallow assigning 16-bit applications through the procedure described above. This can be worked around manually, as follows:

  1. Use Start, Run, type CMD and click OK to open a command prompt.

  2. Type:

    assoc .ext=Filetype

    where .ext is the file extension and Filetype is the file type mnemonic. Filetype can be chosen somewhat arbitrarily, but it should not conflict with an existing file type.

    For example, to associate QA Write (*.QW) files, type:

    assoc .qw=QAWrite

  3. Next type:

    ftype Filetype=Executable %1

    where Filetype is the same as that used in the assoc command and Executable is the full path to the program you wish to use.

    For example, to associate QA Write files, type:

    ftype QAWrite=C:\Program Files\QAWIN\QAWrite.exe %1

  4. Close the command prompt.

Removing Custom Assignments

Windows can also store associations for file types on a per-user basis. These generally over-ride those set via the shell (Default Programs) or ASSOC/FTYPE. Unless there is a special reason, these should be removed. Use Registry Editor and browse to HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts and delete or rename the key for the desired extension.

Other Information

Some programs have in-built functions to assign certain file types to themselves. For example:

  • Windows Media Player 9.0

    Go to Tools, Options, File Types. Select all the file types you wish to be handled by Windows Media Player (or click Select All) and click OK.

  • Apple Quicktime

    Go to Edit, Preferences, Quick Time Preferences. Select File Type Associations. Click File Types. Choose the file types you wish to be handled by Quicktime or click Use Defaults.

  • Jasc Paint Shop Pro

    Go to File, Preferences, File Format Associations.

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