In Windows 8.1 > Control Panel > Default Programs > Set your default programs I am unable to make changes to my default programs.


Examples:


Control Panel > Default Programs > Set your default programs > Skype for desktop > Choose defaults for this program I am unable to remove the check mark from CALLTO URL: Callto Protocol


Control Panel > Default Programs > Set your default programs > QuickTime > Choose defaults for this program I am unable to remove the check mark from .midi


Why am I not able to remove these check marks?