Note: First I recomend reading up on how to choose the best registry cleaner
RegCure PC Optimizer
The RegCure PC Optimizer by ParetoLogic is fast, very easy to use, has a ton of features, and has great customer service. It found a lot of errors and removed all of them, making my computer noticeably faster. Another great thing about it is that it allows you to customize the way the program scans your computer, and that it doesn't take up too much memory which allows you to use your computer for other things while the software performs the scan. Download a Trial of RegCure PC Optimizer
Symantec PC Tools Registry Mechanic 9.0
The Registry Mechanic 9.0 is a very good program. It is pretty easy to use. It found lots of errors on my system and removed most of them. My computer was definitely faster after the scan then it was before. It is also fast and doesn't take up a lot of memory so you can do other things while it scans your pc which I found useful. However, the customer service was pretty bad.
WinCleaner One-Click
This is also a very good registry cleaner. WinCleaner does everything as advertised. It was easy to install and use. It is fast and is able to fix all computer problems. It also has many different options which allow you to either run the scan with one click or perform a customised scan where you can tell the program which files you want don't want scanned or deleted. This program was tested on a very old windows computer, and it made it perform almost like new.