Ben Fathi in a blog post explains about User Account Control (UAC) in Windows 7 — UAC is a feature that crosses many aspects of the Windows architecture—security, accounts, user interface, design, and so on. In the course of working on Windows 7 we have taken a hard look at UAC – examining customer feedback, volumes of data, the software ecosystem, and Windows itself.
“UAC is really about informing you before any “system-level” change is made to your computer, thus enabling you to be in control of your system. An “unwanted change” can be malicious, such as a virus turning off the firewall or a rootkit stealthily taking over the machine. However an “unwanted change” can also be actions from people who have limited privileges, such as a child trying to bypass Parental Controls on the family computer or an employee installing prohibited software on a work computer.” […]