How do you remove a default program association for file types in Windows 7?

I somehow have set the default file type association for a file type in Windows 7. It doesn't appear to be possible to delete it from the "Change the file type associated with a file extension" options screen. Is it possible to remove it?

Solution 1:

1. Find the file extension in question under this key in the registry:

   HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts

   Deleting the sub-key with the same name as the extension you want to un-associate will delete the default program association. In older Windows versions, you'll have to kill and restart explorer.exe for this to take effect (the change is instant as of Windows 10 64-bit).

2. In most cases, you will also need to remove the same sub key from HKEY_CLASSES_ROOT as well.

Solution 2:

Even easier method that I found, it just requires the command line.

1. Open a command prompt with Administrator privileges (right click > Run as Administrator).
2. Run the command assoc .<file_extension> in the prompt. This will give the file type which is associated with the extension. If this command returns File association not found for extension .<file_extension>, it means the extension is not associated with any file type. If it returns an association value in format .<file_extension>=<Some Value> , then go to Step 3.
3. Run the command ftype [FileType]= , where FileType is the file type returned in Step 2.

Special thanks go to My Digital Life for the instructions that I used to figure this one out. They also included a step that disassociates the extension from the file type, but based on what you are looking for, that isn't strictly necessary.

Solution 3:

In Explorer, go to Tools | Folder Options | File Types, find the extension you're looking for, and click Delete.

Or, if Delete is grayed out, click Restore (to set it back to the defaults), then Delete.

Solution 4:

Similar to the top answer, but I find it best to only delete the UserChoice sub-key because you don't need to kill all of the info about the file extension (like the open with list), just the "choice the user selected" (aka-UserChoice). I use a REG file to make it fast to repeat for testing. You can copy paste this, including the version line, and save as a REG file. Just change .ics and .vcs to whatever extensions you want (or just remove one line if you only want to reset one):

Windows Registry Editor Version 5.00

[-HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.ics\UserChoice]
[-HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.vcs\UserChoice]

If you aren't familiar with REG files, the above lines that start with "-" simply delete those keys from the registry.

Also, and the main reason I posted this answer, with this solution I don't have to restart explorer.exe. Maybe something specific to my setup, but I've used on Win7 and Win8 and never had to restart explorer.exe for the change to take effect.