Due to its importance in keeping your PC operational, there are many reasons why the registry may experience problems. Perhaps the most common cause of registry problems is frequent program install and uninstall. When you install a new program on your PC many entries are added to the registry to enable the program to function as required. When you uninstall, these entries are supposed to be deleted. However, many times, applications leave behind orphan registry keys and vacant placeholders in the registry which add to the clutter and size of the registry. If an application is faulty or you perform an incorrect uninstall, many errors related to shared DLL, COM, ActiveX control, and incorrect file associations may also arise.
Many times, when you install a new version of an application over an old version, older registry entries—no longer required—may not be removed. Moreover, the new version may add copies of entries that already exist on your computer. This increases the number of obsolete and redundant keys in the registry.
If you are an avid Web user or you frequently get files and data from external sources, your PC can become vulnerable to virus and spyware infections. These malicious programs also add numerous malicious registry keys—including non-removable embedded keys—in the registry.
Eventually, all these problems severely damage and corrupt the registry and thereby start generating frequent system errors and system freezes. In more severe cases, registry problems may even render your system unbootable.