Is it helpful and how often should it be done and are there good registry cleaners?

I don’t want to manually regedit search and destroy references to programs I’ve removed. Can’t registry cleaners do that for me?

how to clean register?

is there any freeware registry cleaner software?

It must be totally free with no hidden surprises. Nothing that only cleans a couple of items and then asks you for payment to clean the rest. It must be completely free.