/Regserver and /Unregserver that created or deleted the required registry settings. COM applications that break because of DLL Hell issues can commonly be repaired with RegSvr32.exe or the /RegServer switch without having to re-invoke installation programs. Advanced functionality Windows exposes APIs that allows user-mode applications to register to receive a notification event if a particular registry key is changed. APIs are also available to allow kernel-mode applications to filter and modify registry calls made by other applications. Windows also supports remote access to the registry of another computer via the RegConnectRegistry function if the Remote Registry service is running, correctly configured and its network traffic is not firewalled. Security Each key in the registry of Windows NT versions can have an associated security descriptor. The security descriptor contains an access control list (ACL) that describes which user groups or individual users are granted or denied access permissions. The set of registry permissions include 10 rights/permissions which can be explicitly allowed or denied to a user or a group of users. As with other securable objects in the operating system, individual access control entries (ACE) on the security descriptor can be explicit or inherited from a parent object. Windows Resource Protection is a feature of Windows Vista and later versions of Windows that uses security to deny Administrators and the system WRITE access to some sensitive keys to protect the integrity of the system from malware and accidental modification. Special ACEs on the security descriptor can also implement mandatory integrity control for the registry key and subkeys. A process running at a lower integrity level cannot write, change or delete a registry key/value, even if the account of the process has otherwise been granted access through the ACL. For instance, Internet Explorer running in Protected Mode can read medium and low integrity registry keys/values of the currently logged on user, but it can only modify low integrity keys. Outside security, registry keys cannot be deleted or edited due to other causes. Registry keys containing NUL characters cannot be deleted with standard registry editors and require a special utility for deletion, such as RegDelNull. Backups and recovery Different editions of Windows have supported a number of different methods to back up and restore the registry over the years, some of which are now deprecated: System Restore can back up the registry and restore it as long as Windows is bootable, or from