What Is User Account Control (UAC) in Windows?
UAC is a security feature of Windows Vista, Windows 7 and Windows 8 which helps prevent unauthorized changes to your computer. These changes can be initiated by applications, viruses or other users. User Account Control makes sure these changes are made only with approval from the administrator. If the changes are not approved by the administrator, they are not executed and Windows remains unchanged. It is as if nothing happened.
How Does User Account Control (UAC) Work?
In modern editions of Windows, applications run by default without any administrative permissions. They have the same permissions a normal user account has: they cannot make any changes to the operating system, its system files or the machineís registry settings. Also, they cannot change anything thatís owned by other user accounts. Applications can change only their own files and registry settings.
When an application wants to make a system change like: modifications which affect other users, modifications of system files and folders, installation of new software, an UAC prompt is shown, asking for permission.