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I am using a certain file type (.QTZ) which I have successfully linked to an application. When I double click, the correct application starts. However, in Windows Explorer, it still says it is a "QTZ File".

How can I change that type description? I have found the "Default Programs" tab in the Control Panel, but it only lets me edit associations, not file types.

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3 Answers 3

up vote 13 down vote accepted
  • Launch regedit.


  • In HKEY_CLASSES_ROOT, find your extension (you just have to type .qtz). Example with .ods file:


  • Look for the Data of the (Default) value (in my case, opendocument.CalcDocument.1, but in yours, something related to your application), and find this name in HKEY_CLASSES_ROOT again, by typing the first letters. Example with opendocument.CalcDocument.1:


  • Change the Data of the (Default) value to the description you want.


  • Close regedit.

To see your changes appear, you can either reboot, or change the default association of some file by choosing "Open with > Choose default program..." (I couldn't find the proper method). Here is the result:


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The solution proposed by m4573r used to be the only way to do this up to Windows XP but doesn't always work in Windows 7 if file extensions are first associated with a program from Explorer (when using "Open with >").
In such cases you might have to navigate to the following registry key:
and change the (Default) value directly under your file extension registry key.

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All my video file types were "MediaPlayerClassic-HC" files, regardless of the extensions (mov, mp4, wmv etc...). To avoid this, you should associate the files directly in MPC-HC "View/Options/Formats" instead of using "Open With" and "Choose Default" in Windows Explorer.

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