User Account Control: Inside Windows 7 User Account Control

This article from Mark tells you everything you did not know about UAC.

User Account Control: Inside Windows 7 User Account Control: "Standard user accounts provide for better security and lower total cost of ownership in both home and corporate environments. When users run with standard user rights instead of administrative rights, the security configuration of the system, including antivirus and firewall, is protected. This provides users a secure area that can protect their account and the rest of the system. For enterprise deployments, the policies set by desktop IT managers cannot be overridden, and on a shared family computer, different user accounts are protected from changes made by other accounts."