What is the BEST Registry Cleaner for Win 7 Ultimate or Pro 64 Bit version OS ?

Country Boy you should only use certain programs that do work. But you have to have an advanced knowledge of the os system you are using.  For instance, say the program find a part of an registry that used to belong to a program but is shared with another , maybe say a game or your os system. 

Deleted or repairing that registry with out taking further steps to prevent mishap could cause serious problems that only a clean boot can cure of even worse.  the fact that you are asking about a program to use with window pro 64 tells me that you don't have the skillset to accomplish a successful optimization of you system And I would recommend using the action center  and your help section for your needs.  Have you ever thought that you might have a trogen that is invisible to most security programs.. I would try microsoft Malicious malware remover first and listen to these guys.

I agree with you that pre-Windows 7 a registry cleaner can often reduce problems.

However with the advent of Windows 7 and subsequent versions, the registry is constructed differently, and applications access the registry in a different manner, therefore the fact that it's "untidy" is of no consequence at all, and isn't worth bothering about.

By the way I wonder if this theory you have, also applies to  the folks who are still running Windows XP. I sure would hate, "today", to see the  years of accumulated TRASH they have acquired. I used the word "today" because 11 months ago I had to clean up a customers REGISTRY. Yes, I had a good registry cleaner to accomplish that task. I purchased it on the internet, it was from England. This customer had accumulated Megabytes of trash!!. And a trashy registry does slow down a system.