CCleaner - Clean Regedit?

Has anybody tried clicking the regedit box in ccleaner and press clean? What does it clean of regedit?

 

I am completely confused. Perhaps you could post a screen print to show what you are writing about?

 

If it is the option PeteC is referring to ..
Cleans out MRUs (Most Recently Used). So when you click on the "down arrow" in regedit view, it will be empty ... at least that is what it did when I tried it about a year ago. I unticked it because I like to have the list available .. but that is my preference.

 

Or if you mean the registry cleaner option itself, it finds leftover pieces of old programs like missing file associations, missing dll's, wrong path, ect. Works pretty well and I have never read of it causing any problems. Plus it gives you the option to make a backup first.