The Windows registry is a database repository of information about a computer's configuration. Installing and uninstalling software will make your registry a mess, leading to decreased PC performance and causing computer crashes. The registry size keeps growing when you use Windows. When the registry becomes very large, your computer's performance will be decayed and unstable. Some computer users even spend a lot of time trying to go through the registry and edit it manually. Not only can this be a daunting task, it is also a risky one.