Editing Windows Registry (section)

== Virtualization ==

=== INI file virtualization ===
Windows NT kernels support redirection of INI file-related [[application programming interface|APIs]] into a virtual file in a registry location such as HKEY_CURRENT_USER using a feature called "InifileMapping".<ref>{{cite web|url=http://www.microsoft.com/technet/archive/ntwrkstn/reskit/26_ini.mspx?mfr=true|title=Chapter 26 – Initialization Files and the Registry|publisher=[[Microsoft]]|access-date=2008-03-03}}</ref>  This functionality was introduced to allow legacy applications written for [[16-bit]] versions of Windows to be able to run under Windows NT platforms on which the System folder is no longer considered an appropriate location for user-specific data or configuration. Non-compliant 32-bit applications can also be redirected in this manner, even though the feature was originally intended for 16-bit applications.

=== Registry virtualization ===
[[Windows Vista]] introduced limited registry virtualization, whereby poorly written applications that do not respect the [[principle of least privilege]] and instead try to write user data to a read-only system location (such as the HKEY_LOCAL_MACHINE hive), are silently redirected to a more appropriate location, without changing the application itself.

Similarly, [[application virtualization]] redirects all of an application's invalid registry operations to a location such as a file. Used together with file virtualization, this allows applications to run on a machine without being installed on it.

[[Mandatory Integrity Control|Low integrity]] processes may also use registry virtualization. For example, Internet Explorer 7 or 8 running in "Protected Mode" on Windows Vista and above will automatically redirect registry writes by ActiveX controls to a sandboxed location in order to frustrate some classes of [[Exploit (computer security)|security exploits]].

The Application Compatibility Toolkit<ref>{{cite web|url=https://technet.microsoft.com/en-us/appcompat/aa905102.aspx|publisher=[[Microsoft]]|title=Microsoft Application Compatibility Toolkit 5.0|access-date=2008-07-26}}</ref> provides [[shim (computing)|shims]] that can transparently redirect HKEY_LOCAL_MACHINE or HKEY_CLASSES_ROOT Registry operations to HKEY_CURRENT_USER to address "[[Principle of least privilege|LUA]]" bugs that cause applications not to work for users with insufficient rights.