There are two occasions when you are tempted to buy a registry cleaner.
The one I concentrate on in this article is when you suspect the computer has been infected. The other is when you get tempted by the idea that a registry cleaner will not only tidy up your registry, but also will leave your machine running faster.
My advice is if it isn't broke, don't fix it. I accept that all registries have unnecessary or unused settings, but I also accept that this extra baggage does not matter. These extraneous values have negligible effect on the computer's speed. If you try and find ALL the unwanted values, it will drive you mad. Worse still, sooner or later you will get carried away; you will make a mistake and remove a setting that the operating system needed. My point is there is no need to buy a Windows 8 registry cleaner.
Have you ever thought about how registry cleaners work? They have numerous logic routines that look for registry settings that are no longer needed. But what if they are out-of-date or your machine has a combination of programs not covered by its scripts? The result could be it deletes registry keys that are actually needed by your programs, the result your applications now run slowly!
Root Cause Analysis
If a registry cleaner won't solve your computer problem, then what will? Here are my 8 for Windows 8 troubleshooting techniques.
1. Don't run more than one anti-virus program, installing a second anti-virus program is a prime cause of a machine running slowly.
2. The oldest troubleshooting tip is to uninstall any programs that you added just prior to the onset of the problem.
3. What news of your Windows Update? Sometimes an update does not complete, or just needs a reboot. Check Control Panel, System and Security, Windows Updates, look for any items with Status: 'Failed', and retry.
Secunia is also a great free utility for detecting missing security patches on your computer.
4. Check the event logs yourself. Could it be that a hard disk is failing? Search for Event Viewer, and use it to examine the Windows System log; I prefer to filter for Error and Critical. Repeat for Application log.
5. Another of my favorite troubleshooting tools is the Task Manager. My technique is two-fold; sort on CPU so you can observe which process is hogging the processor. Examine the list of processes; do any appear to be malware? I know it's difficult to know good processes from rogues, but if you research any that look suspicious on the internet then you may be able to identify the problem.
6. One underused troubleshooting technique is to compare the stricken machine with a similar Windows 8 machine that is working properly. A second machine can also provide a lifeline if you need remote registry editing.
7. While I would not buy a Windows 8 registry cleaner, that does not mean that I would not use other tools to troubleshoot. It's become unfashionable to use Microsoft's own free tools such as Security Essentials, but I have seen the company change from seeming not to care about malware, to being like a protective mother wanting to care for the baby Windows 8 (Malicious Software Removal Tool).
8. If there is a rogue registry setting then it will leave a signature, symptoms or clues how to fix. Someone somewhere will have seen it before, and blogged removal instructions. Under these circumstances you need to have a progression, try regedit in normal mode, then boot into safe mode and try regedit there. As a last chance, I would try remote registry editing.