What is UAC?
UAC aka User Account Control is a security control feature of Microsoft Windows Operating Systems introduced in Windows Vista.
What does UAC do?
User Account Control, or UAC for short, controls the access level and priviledges of programs running on a Windows PC. By default it gives running programs a standard user's priviledge level and access to the operating system resources.
If a program needs Administrator-level access and permissions then the UAC will pop-up a message window asking you if you wish to give the program such permission.
When introduced in Windows Vista, UAC was enabled by default and would annoy users by constantly asking them if a program can have higher access, or if you are sure that you wanted to perform the requested action. This annoyed users so much that UAC played a large part in the lack of popularity for Windows Vista.
You can turn off UAC if desired, but if you can live with the pop-ups then it is advised to leave it enabled from an added security perspective.
UAC has been much improved in Windows 7.
Article date: 26th February 2011