The Windows registry is a large database that contains the settings and configurations for hardware, programs and applications running on your computer. Whenever you install programs, its keys and values are embedded in the registry, where you can configure them or perform troubleshooting steps to repair damaged programs. If the registry is not properly maintained, it can suffer errors that cause system and application problems.
Registry errors can be caused by improperly uninstalled applications that leave registry entries that cause start-up problems. Viruses, Trojans and spyware are also known to cause registry errors because they install registry entries that are very difficult to remove manually. They also change file associations and prevent you from opening executable files. Registry errors are also caused by a vast number of unnecessary files on your computer system that use system resources with no added benefit.
The "Blue Screen of Death" is a common type of registry error. When the settings are improperly configured on the registry, the computer crashes and displays this frequent blue screen error as a result of registry errors. DLL errors are other common types of registry errors that occur when an application is missing a vital DLL file that helps run the executable files of that application. Registry start-up errors are other common registry errors. These errors usually occur when a start-up item is missing or improperly configured.
Registry errors cause the overall system to slow down. Because the registry is the central configuration center for programs and system components, any errors cause slow start-up and shutdowns. Registry errors cause applications to slow down, freeze and eventually crash. Registry errors also reconfigure boot options and prevent your PC from booting up. Registry errors are also known to cause network errors, especially if there are malware entries that create network intrusions.
Prevention and Solutions
Properly uninstall programs and applications you do not use. While most programs can be uninstalled from the "Add or Remove Programs" window on the Control Panel, others must be uninstalled using a removal tool supplied by your software's manufacturer. Run frequent virus scans, and delete malicious files that install on the registry and cause programs to crash. Fix registry errors with free registry cleaning tools such as CCleaner, Glary Utilities and BleachBit (see Resources below). Registry cleaners remove unnecessary registry entries and repair ActiveX and missing file extensions.
Never download programs, games or applications from unauthorized websites. Many of the downloads on such sites are bundled with Trojan viruses that install entries in the registry. Unless you are a trained professional, never try to manually fix registry errors; you're likely to seriously damage your computer's functionality. Always back up the registry so you have a restore point you can come back to in case of system errors.