There is a file you can find in ~/Library/Preferences/com.apple.LaunchServices/com.apple.launchservices.secure.plist
In there, you will find a dictionary entry similar to this:
<dict>
<key>LSHandlerContentType</key>
<string>public.folder</string>
<key>LSHandlerRoleAll</key>
<string>com.apple.quicktimeplayerx</string>
</dict>
Which you will want to remove. Save the file, then restart the computer.