A registry cleaner is a class of third party software utility designed for the Microsoft Windows

operating system, whose purpose is to remove redundant items from the Windows registry.

Registry cleaners are not supported by Microsoft, but vendors of registry cleaners claim that they are

useful to repair inconsistencies arising from manual changes to applications, especially COM-based

programs.

The effectiveness of registry cleaners is a controversial topic, with experts in disagreement over their

benefits. The issue is further clouded by the fact that malware and scareware are often associated

with utilities of this type.

https://en.wikipedia.org/wiki/Registry_cleaner