As long as you would somehow interact with files with .amr and .dct formats, they will keep reappearing on when you scan for Registry issues on CCleaner. Relax, those issues won't do any harm in your computer as far as I'm concerned to just add them to the Exclude list. so the next time you see them detected as a Registry issue, just right-click them and choose Add To Exclude List. I experience the very same thing with my .themepack files. CCleaner has been able to mark those as issues in the last 3 versions since its Registry cleaner got more aggressive in the last 3 versions.