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?

Answer

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.