Hi, Ccleaner once analyse would have asked you if you want to clean on computer and application cleaning. After you run registry clean, it will ask you, if you want to create a restore point. So, as above advised, do create a restore point, and then clean. if any problem, you could revert to restore point to save the computer.But so far as me, i will believe it clean everything.
There is also a possibility of deleting individual keys. The ccleaner will give the suggestion, and then you can keep those entries or not. Good luck. The ccleaner cleans, but the allone tools in this tweaking com protects all your windows file and a wowwre wow is a useful tool for computer handlers, who has to individually download fixes from anywhere. It is a quick fix for most of the windows problems.