when was control a implemented in windows
Figure 1. Percentage of machines (server excluded) with one or more user accounts from January 2008 to June 2008. User Account Control was implemented in Vista to address two key issues: one, incompatibility of software across user types and two, the lack of user knowledge of system-level changes. We expanded the account types by adding the Protected Admin (PA), which became the default type for the first account on the system.