Because the bad info that always surfaces when a registry cleaner is on GOTD gets to me. [sigh]
Software to clean Windows registry is limited to deleting history &/or cache entries and deleting broken links. To remove leftovers from uninstalled apps the software would need to have records of what currently & previously installed software added to and/or changed in the registry. Some uninstaller apps can monitor software installations to try and overcome that, while others can use data that’s been previously recorded, usually either for specific apps, e.g. security software, or for a selection of more common, popular apps. Registry cleaners cannot remove useless &/or unused entries, because there’s no rules that they can use to determine just which entries are useless &/or unused. All of these solutions are limited, because there are some changes to the registry that are dangerous to try and reverse, and some that just can’t be reversed, so registry cleaners and uninstallers generally won’t let you do anything that might be even slightly risky or unsafe. When someone has a problem after running a registry cleaner, it’s usually because of software, including drivers, relying on registry entries that strictly speaking, shouldn’t be there, e.g. a link to something that earlier versions of an app needed but is no longer valid.
[Note: I edit the registry manually to clean it up because of those factors, though I wouldn’t recommend it because it can take so very long – once or twice I’ve spent more than one day. If a registry cleaner deletes an entry that points nowhere, the rest of the key remains; it’s better to lose the entire key when possible, getting rid of sometimes a half dozen or a dozen lines instead of just one. To try and avoid that drudgery I’m also picky about what software gets installed, monitoring just what an installation does using a VM, and often bypassing all or parts of the installation routine to reduce the amount of garbage that’s added.]
There’s really nothing about this that’s terribly complicated or magic. The registry itself is made up of several files [called hives] that form a central repository where data can be stored for Windows and any installed software. While Windows is running it’s constantly reading & writing to the registry – other installed software may or may not do the same. A copy of Vista or Windows 7 that’s had lots of software installed, updated, and removed over the course of years can sometimes have a registry that’s very large, bloated, and does in fact slow things down. Microsoft’s long-time recommendation was to periodically delete that copy of Windows and reinstall it fresh. Windows 10 – except for the fall 2019 update if you’re already running the Spring 2019 version – is essentially replaced every 6 months or so, and lots of accumulated garbage in the registry is not carried over, tending to eliminate that problem.
The biggest problem with the registry itself is that there are no enforced rules on what data can be stored there, or how and where it should be stored. Complicating things, some software has been updated for years and years, building on parts of the original version’s core programming [including Windows]. Because stuff can be buried in the old code that’s a foundation for today’s version, software may look for a registry entry or entries that have no current function, or they may have problems because of something an older version left behind. Running software to clean the registry can both fix and cause problems because of that.
An entry in the registry might point to a file or another registry entry in a specific location that does not exist, but an app may include old code that looks for that entry because it used to matter. When software cleans the registry it’ll likely find and want to delete what appears to be a worthless, broken entry, but once it’s gone, the software that looks for it might break. And sometimes that’s actually a good thing – sometimes an old app, or parts of it, are causing problems, and so breaking that app makes those problems go away. It’s also possible that a registry entry left behind by an old app or old version of a current program can confuse the current software [that’s somewhat frequently a problem for example with graphics drivers].
Cleaning the registry, either manually – using Windows Regedit or similar, and modifying or deleting entries yourself – or with software, there’s a chance that something, including Windows might break. If you use disk/partition image backup software, e.g. Macrium Reflect [Free or Paid], and can easily restore a backup, that’s probably the easiest option to use as a failsafe. Otherwise you might want to check out the registry backup app at tweaking[.]com [ tweaking[.]com/content/page/registry_backup.html ], paying attention to the documentation so that you can restore that backup if Windows won’t start. You can export parts of the registry using Windows Regedit, and easily merge that data back into the registry [usually just by double clicking the exported .reg file], but you can’t back up the complete registry that way. And like using the backup feature of any registry cleaning app, Windows must be running to restore anything to the registry.
That all said, too many people have reported positive results after using various registry cleaners, &/or uninstall apps that include them, to say that it’s all some worthless hoax. At the same time, the copy of Windows you’re running is likely unique – no one else running the same version of Windows on an identical device has installed, & possibly removed the very same software that you have – so expect that mileage will vary, and you may or may not experience any improvements. For that same reason, *if* I had an older copy of Windows that had seen some software churn, any testing I performed could only be relevant to that one copy of Windows, so I haven’t tested today’s or last week’s registry cleaner giveaways. If you can easily put things back, e.g. restoring a backup, nothing ventured, nothing gained. If you don’t want to bother with any safeguards, e.g. backing up, then risks vs. possible rewards are solely up to you.
There are naturally myths and legends…
Some will say the registry can’t cause problems, that its size is irrelevant and so on… that’s simply FALSE. There are loads and loads of things that effect Windows performance, and sometimes the registry causes problems, sometimes not. If using a registry cleaner didn’t fix your copy of Windows, there’s no reason to say it won’t help someone else’s. On the other hand, registry cleaners cannot fix every possible problem in Windows registry, so if you use one and it doesn’t help, that doesn’t give the registry a clean bill of health either. If you’re having problems with a copy of Windows, *That’s what matters*, and a registry cleaner is just one of many options you can try in your efforts to fix it.
FWIW -- Debunking some [IMHO inaccurate] comments…
“Ok, having now tried the programme, and seeing that it's telling me I have more than 7,000! reg entries to be removed, can only say "Are they nuts?" and move on.”
OK, installing just one program can easily add 4 times that, if not more. And a portion of the 7k is likely cache. If numbers like 7k & larger scare you, there’s nothing wrong with shutting a registry cleaner down then and there, but those numbers are not unrealistic. In fact, you have to delete many thousands of entries before you’ll notice a small but real difference in the size of the registry.
“No matter how many hundreds or even thousands of so called errors registry cleaners find, deleting them is usually pointless.”
It’s simply a matter of magnitude – Windows has to read [load] the registry, and then modifies it constantly, and I’ve personally seen cases where it became large enough to slow things down.
“Today's giveaway, just like at least 99% of other registry cleaners, will sometimes mistakenly think that valid registry keys are errors and want to delete them.”
These apps look for broken links, e.g. a registry entry pointing to a file or another registry entry that isn’t there – by definition a link that points nowhere is broken, and likewise an entry that’s broken cannot be valid. However, as I noted above, old programming code still present in a newer version of an app may check to see if an entry exists, even though it’s no longer valid or used. It doesn’t happen that often, but it does happen.
“System Internals from Microsoft which is free identifies the start up issue and allows you to deselect it to see the improvement.”
Use Autoruns with Extreme Caution – it was never intended to be a tool for casual users. Autoruns lists everything that starts when Windows does and has the option to move *Some* of the registry entries that start this stuff to a new registry key that Windows doesn’t know about, and so doesn’t look for. It does not prevent you from stopping something that Windows needs in order to start, and sometimes it’ll move one registry entry when Windows uses two or more, which can also break Windows.
“Registry files are very small and do not consume much in the way of storage space. Unless you are an expert user it is not a wise thing to interfere with these files, removing the wrong registry file(s) can severely damage your system. Windows "knows" which files are valid or invalid and will simply ignore the redundant files, so-called registry cleaning will not improve your systems performance. In my experience the only time invalid registry files cause problems is when the user has attempted to modify them. Best advice is if it ain't broken don't fix it.”
WOW – where to begin… Windows registry can grow quite large, but size is relative – it’ll never be as large as the movie on a Blu-ray – and the issue is not how much hard disk space it takes up, but rather does Windows on a particular device have problems due to the registry’s size. You’ll Never remove a registry file – if you did you just destroyed that copy of Windows. Windows Does Not keep track of any files, valid or invalid, and wouldn’t know if there were any redundant duplicates. The way it works is Windows will go to use a file – the instructions to do so might be hard-coded or in registry entries – and if it doesn’t find it immediately it will *sometimes* search for it. None of which has anything to do with registry cleaners. If a registry entry [Not File] was invalid, you should be able to do anything to it you wanted, including deleting it, the exception being as noted previously, if/when an app looks for it. When it comes to “If it ain’t broke…” the snarky reply might be “how would you know if it was?”. Setting snark aside, while it can of course lead to nasty consequence, e.g. through greed, desiring something better is a huge part of just being human, and is at the core of every advancement we’ve made since our ancestors lived in caves. I can understand that comment’s author avoiding something beyond their capabilities, but to assume everyone else is just as incapable is beyond silly.
[And from the same person] “In all my years as an IT Technician, the only times I ever come across system issues caused by bad or corrupted registary enteries is because the user has tampered with registry files and messed things up. Registry files, take up very little space on your drive and Windows will simply skip over any redundant or unreadable registry files it comes across. Attempting to fix corrupted registry files is something that should be done by an expert user with a sound knowledge of what they are doing. Programs such as this could potentially do more harm than good and in some instances will remove vital registary files.”
Another WOW! Any idiot can work on PCs & such – too many do. Yes, a user can delete needed entries in the registry, and they can change values, and both can cause problems, but it’s terribly hard to add a bad registry entry, since software will most probably ignore it, and there’s no such thing as a corrupted registry entry. If a registry hive file is corrupt [e.g. the hard drive went bad], Windows is broken, and that corrupted hive file is the only way you’d have an unreadable registry entry. In any case the [only] fix is easy – restore a backup, to a good disk if necessary, or (re)install Windows. A redundant registry hive file isn’t going to happen – Windows looks for those files in specific places, and you can’t have two files with the same name. It works the same way with registry entries; software looks for values in specific places, and you can’t have 2 registry keys next to each other using the same name. No one has ever tried to reduce the file sizes of the registry hives to save disk space – if it becomes too large & bloated it can slow things down when loaded into RAM, especially if there’s not enough available.
“Cleaning registry may be needed if malware has written nasty code into your registry.”
A registry cleaner would most likely be useless in this situation. If there’s a link to run the malware, it’s working, just like any legitimate app, so a registry cleaner would leave it alone; it’s true though, that if you removed the malware, might as well remove any links in the registry that were pointing to it. If OTOH malware stores snippets of code as registry entries, registry cleaning software wouldn’t know to spot it.
“By the way, some well known software such as Acronis 2011 does offer you to "integrate Acronis backup with Windows 7 Control Panel". If you click [Yes], it will do so and the change is PERMANENT. Even if you uninstall Acronis 2011 later on. That is, Acronis (after you gave permission) writes to the Registry changes that cannot be undone.”
Like most software, Acronis simply does not have an uninstall routine that's 100% complete – there’s nothing permanent about it. [In this case I suspect you simply have to delete the .cpl file in C:\Windows\System32\.]
“The best registry cleaner is no registry cleaner. I can't think of a faster way to trash your system than to do deep registry cleaning.”
Then you have a Very limited imagination. The registry can become bloated and large enough to sometimes cause problems. Individual entries in the registry can also cause problems, though it’s doubtful cleaning software will spot them all.
“Setting a restore point and/or backing up would be a wise precaution before trying one.”
Backing up yes – a Restore Point, Not so much. If you get into the deep end working with Windows, you’ll probably have to undo stuff that didn’t work. And if you’ve done much of that, you’ve found that restoring a restore point does not always work.
“There is no need to ever clean the registry. It is exceptionally rare for cleaning the registry to make a computer run faster or fix any other issues you are having, no matter how many hundreds or thousands of errors are found. If your computer is running much slower that it should, or you have some other issues with it, then in my exprience, around 99.9% of the time, a registry cleaner won't help.”
This might have been better phrased to say that the author hasn’t personally experienced noticeable benefit from running a registry cleaner, which is a completely valid statement. There is no basis OTOH to say the registry *can never* benefit from being cleaned, nor for the somewhat contradictory statement that maybe sometimes, but rarely.