I updated (upgraded) from Windows 8 to 10 a few months back.
Ccleaner was deleted from the list of programs. Yeah, MS doesn't like things that can tamper with the registry.
I re installed it, from scratch. Pi$$ed me off a bit. Lost my .ini file with the new install.
I later realized I could have reinstalled it (or rather, restored it) from the list of programs somewhere in the old files - I forget where they were kept/how to get there - I'd just googled the issue and found the answer.