I did a basic comparison of 5 registry cleaners. I ran them on a new install of Microsoft Windows XP Professional, version 5.1.2600 Service Pack 3 Build 2600. Not connected to the Internet, no updates done, just out of the box with only these 5 programs installed.
I take it for granted that the system as delivered by the Windows install doesn't contain any serious errors. If I had continued with the system I would have done all necessary Windows updates, installed my application programs and probably have had a nicely working system for years to come, without doing anything to the registry.
Three of these programs combine the registry cleaning with other functions like file and history cleaning (also called 'privacy cleaning') and various optimisations. For these three I only looked at the registry cleaning functions.
Two only clean only clean the registry, and are cheaper.
Anvi soft Clo ud Sys tem Boos ter v1.1.1 (remove the spaces)
Result: 400 errors. That sets the record!
PC Tools (by Symantec) Registry Mechanic (no version shown, downloaded August 2012)
Showed the system status to be very bad (deep in the red area of the graph), which clearly is nonsense for an unchanged clean install.
Result: 22 errors
Reg zooka (no version shown, downloaded August 2012)
Result: 220 errors found (152 of them being empty keys, which don't harm at all)
(however, see http://forums.cnet.com/7723-6122_102-541753/regzooka-fraud/?tag=mncol;1f)
Uniblue Registry Booster 2013
http://download.cnet.com/Registry-Booster-2011/3000-2094_4-10510869.html?tag=mncol;2#editorsreview is the review for the 2011 version
http://www.uniblue.com/nl/software/registrybooster/ downloads the 2013 version
Result: 45 errors (barometer deep in the red also, which clearly is nonsense)
WinASO Registry Optimizer 4.7.7 http://download.cnet.com/WinASO-Registry-Optimizer/3000-2094_4-10260558.html
Result: 48 errors
As I said above, I don't expect any of these errors to be serious errors. I can't say they are no inconsistencies and errors in the registry, but I'm convinced they don't harm anything and don't need correction.
All these programs will find many more "errors" in the registry if you run them on a system that you used for some time and installed and uninstalled programs on. Most of these will be just as harmless as the ones above found on a totally clean system.
From running these programs I have some tips for you, if you feel your registry really needs to be cleaned. Most members and moderators here (including me) believe that that never is the case, so we don't use these programs, but just in case you're convinced of the opposite and even want to pay for them (they are around USD 30) here are my tips:
- Don't use any program that sets itself to run at boot or schedules itself to run every day. It really isn't necessary to do that and would offset most performance wins the cleaning does.
- Only use programs that allow you to undo what they do, just in case they mess up. The least you can expect is that they have the option to make a system restore point before changing anything (just in case you forget to do it yourself), but that includes more than just the registry. So it's better if they have their own dedicated undo.
- Don't run it too often. Once every few months should be enough.