"User Account Control (UAC) is a technology and security infrastructure introduced with Microsoft's Windows Vista and Windows Server 2008operating systems, with a more refined*[1] version also present in* Windows 7 and Windows Server 2008 R2 . It aims to improve the security of Microsoft Windows by limiting application software to standard user privileges until an administrator authorizes an increase or elevation. In this way, only applications trusted by the user may receive administrative privileges, and malware *should be kept from compromising the operating system. In other words, a user account may have administrator privileges assigned to it, but applications that the user runs do not inherit those privileges unless they are approved beforehand or the user explicitly authorizes it."

*As per Wikipedia.