there was a tool from microsoft called regclean that I used to use a while back but that was on win98 machines I don't know if they still even make/support it but it worked quite well.
Why not just use the Windows defragger? Also, in my experience, registry cleaners can do more harm than good (i.e. erase necessary entries). If your computer is running slowly, a clean install of Windows works much better.
I agree with erickgwpo. Last time i ran a registry scan with a tool(i don't remeber which one), it actually deleted some of verey important entries, to cure which i had to reinstall windows.
The best registry cleaner would be a clean, new install of windows. The best registry cleaner though would be Glary Utilities. http://www.download.com/Glary-Utilities/3000-2094_4-10508531.html It never deleted or modified any registry entries that kept windows running smoothly. But it only inproved my system performance slightly. Auslogics Boostspeed has all the components to keep your computer running smooth but it cost $$$. Try the free trial and you will be satisfied. Glary utilities also has useful components such as a empty folders finder and duplicate files finder. http://www.download.com/Auslogics-BoostSpeed/3000-2094_4-10358299.html?cdlPid=10840094 Edge