This means some "registry cleaner" deleted entries which are required to launch metro apps. It's not just windows apps, settings has same error. Disabling SIB, issue goes away. I don't use registry cleaners except CCleaner after uninstalling a program. Perhaps CCleaner is the culprit? I'll uninstall SIB with Revo and make sure all registry entries are deleted and reinstall. Thanks for the suggestion and I'll try again.I've used CCleaner for years but indeed, all registry cleaners including the one in CCleaner, cause more harm than good.