You can almost view “Registry Cleaners” as the FDA views products.

For Medicine the FDA requires the product to be both safe AND effective. “Effective” means it has to actually help.

For Supplements the FDA only requires the product to be safe.  What this rule means is that according to the FDA companies can legally sell sugar pills (ie, supplements that do nothing) as long as they are safe.

And with Registry Cleaners both questions are relevant

• safety
• effectiveness

Safety

As for safety, let me quote an expert who’s opinion i trust.  He is, as you’ll see, very safety conscious.  [from a techsupportalert.com forum entry entitled “WinUtilities 9 Free“]:

I have never used any such combo utilities like the ones mentioned on this thread, so I don’t have any idea about them. I have never used registry cleaners, and I don’t intend to use them in the future too. I always see registry cleaning as a process, which has quite a lot of risk involved [emphasis mine -MM], and I think users would be better off without using it.

I like to keep my system clean though, and I don’t like useless things lying around. Once, I had just out of curiosity used CCleaner registry cleaner tool, just to analyze and see what it finds. There were many entries there, for which the corresponding program had been uninstalled. I was tempted to use the cleaner that time, but I decided the risk would not be worth it.

For system tune up, I use CCleaner everyday (without the registry cleaner). I sometimes use disk defragment, but the frequency of using is very low. I sometimes use registry defrag, but only very rarely.

I know MC [another expert i trust -MM] does not use registry cleaner, and advises against it. He does not even use a file cleaner like CCleaner .

Amongst file cleaners too, I only trust CCleaner. I find it very safe. All other file cleaners, look like CCleaner anyways, and some of them can bring down your system, by cleaning important system files.

For average users, I would advise not using registry cleaner at all. Using CCleaner, and disk defragment would be enough. I haven’t used any combo utilities till now, so I don’t know what all is there in them… but I think individual software are there, which perform the job better in that category, like junk cleaning, or managing start up programs.

__________________
Anupam

Effectiveness

And yet, here is another post that represents several users’ experience [from a comment to a techsupportalert.com article entitled “Best Free Registry Cleaner”]:

So I tried [Wise Registry Cleaner and] my whole system snapped to life!

I have no doubt that this kind of result is possible.  It is not at all guaranteed.  There are many things that can slow down a system.  But one of the things is “hooks” installed that point to programs that dont exist.

Eg you might install Some Cool Program, and when you do, it auto-detects that .xyz file is being used, and does something useful.  But if you uninstall Some Cool Program, then the hook that detects .xyz file might accidentally left behind.  Then every time you access .xyz file, Windows spends time trying to find that program, and it doesnt exist.  This can take noticeable time.  Small increments of time that happen repeatedly until you notice that your system is responding slowly.

So a SAFE Registry Cleaner can speed up your system, if you happen to be suffering from that particular problem.

Better SAFE than fast, however.

Before trying a Registry Cleaner, backup your registry, or, to be even safer, get a second disk (another computer, 2nd disk installed, external drive) and use my fav Paragon Backup & Recovery Free to make a backup image of your hard drive. Find that program at techsupportalert.com’s article entitled “Best Free Drive Imaging Program”