The Windows Registry, usually referred to as "the registry," is a centralized database of configuration settings in Microsoft Windows Operating Systems.
The Windows Registry is used as a single place to store much of the information and settings for software programs, hardware devices, user preferences, operating system configurations, and much more.
The Registry is accessed and configured using the Microsoft Registry Editor. Registry Editor can be accessed by executing regedit from the Command Prompt or from the Search or Run box from the Start Menu.
NOTE: DO NOT clean the Windows Registry unless you are sure which entries you are deleting and which entries must remain. Deleting vital registry entries may cause errors in your PC.
Alternatively you may use softwares to help you safely clean your registry: