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If I have a file.class and I opened it with Notepad, how do I destroy that association so that Notepad is not associated with .class? I do not want to change the .class association to another program - just remove it. I use Windows 7.

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… and you don’t even tell us your OS? –  Kissaki Dec 16 '12 at 20:12
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@Kissaki 'Notepad' implies Microsoft Windows –  user49740 Dec 16 '12 at 20:18
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So … which version of windows? :) The steps necessary may differ. –  Kissaki Dec 16 '12 at 20:19
    
I do not want to change the filetype association to another program - just remove it. So what do you want to happen when you double-click it? Do you want the Open with… dialog? What is the extension? How did you create it in the first place? There are several ways and places that an extension can be registered, so getting rid of it will depend on how/where it was made. –  Synetech Dec 16 '12 at 20:27

3 Answers 3

up vote 2 down vote accepted

In a discussion I found, a Microsoft MVP recommended the use of this program, "unassoc.exe", perfect for your needs.

unassoc is a small portable executable, whose only UI elements include a list of all file types with associations on your computer, the ability to select one or more extensions, and the ability to delete the file type associated with that extension.

Unassoc


Also, if you're simply worried about the overhead of having multiple file extensions registered to a program you don't have installed anymore, the registry cleaner bundled with CCleaner can automate this process for you. It can scan for unused file extensions, and delete the relevant registry entries.

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Windows XP

  1. Click on the Start menu with your mouse or press the "Windows" button on your keyboard.
  2. Click on the "My Computer" option in the Start menu.
  3. Click on the "Tools" tab along the menu bar.
  4. Click on the "Folder Options" option.
  5. Click on the "View" tab.
  6. Make sure the "Hide extensions for known file types" is unchecked, so you can see the full filenames in Windows XP, including file type associations.
  7. Click "OK" and close the "Folder Options" window.
  8. Right-click on a file you wish to change.
  9. Click on the "Properties" option in the right-click context menu.
  10. Click the "Open with..." button in the "Properties" window. Note that the file may already have a file type association saved for it (it will display the icon of the associated application). Be aware that the button may be captioned "Change..." instead of "Open with...," depending on the version of Windows XP you are using.
  11. Click on an application to choose a different file type association for your selected file type. You may also click "Browse" if the application you wish to use for your new file type association is not listed.
  12. Click "OK" once you have chosen a file type association.

Via ehow.com

Windows 7

There is no utility to actually remove, other than registry. So, you could use this utility.

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In Windows Vista you click the Start button and select "Default Programs". There are several options -- you probably want "Associate a file type or protocol with a program".

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