Regedit

As a general rule, no you won't harm your system if you remove some software registry entry which is not an important part of windows.

If you remove it using Ccleaner, you can also request a backup for restore if necessary.

The caveats (rare) would be when you remove something that Windows as a rule, expects to be there. For example, a pdf viewer of some sort, a browser, an email handler.
 
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