User Account Control

User Account Control (often abbreviated as UAC) is a feature of Microsoft Windows to prevent unauthorized changes. When the change happens, it asks the user if you have permission to execute the operation, or often the administrator's password (if one is present).

In its early implementation User Account Control was known as User Account Protection (UAP). It could be enabled or disabled through the use of a Start menu shortcut to, rather than through the user control applet within Control Panel. However, the early UAP implementation used a different keyword for the administrator privilege request. Unlike the modern implementation, which uses the keyword "asInvoker," the early implementations used "requireAdministrator" instead. This leads to an inability to run modern programs within builds that used this implementation as they will produce a run-time error. It is possible to modify a program's manifest to use the older keyword to trigger the UAP prompt, in turn allowing the program to run correctly. However, programs that perform an integrity verification (such as setups) will not run due to the program's checksum no longer matching the checksum it is verified against.

Prompts

 * Windows needs your permission to continue.
 * An unidentified program needs to access your computer.
 * This program has been blocked.
 * This app has been blocked for your protection
 * A program needs your permission to continue.
 * Do you want to allow this app to make changes to your device?
 * Do you want to allow this app from an unknown publisher to make changes to your device?
 * Do you want to allow this app from an unknown publisher to make changes to your device?

Windows Longhorn/Vista/7
Windows Longhorn build 4031