User Account Control dialog box - Standard UserIf you're logged on to the system with a Standard User account, you'll see a User Account Control dialog box like the one shown here. As you can see, this UAC supplies the Administrator account username and prompts you to supply the Administrator account's password. Once you type the correct password and click OK, the operation will begin without any other intervention from you.
At this point, I want to point out that the shield icon and the color of the banner on which it sits are important visual cues in differentiating the types of UAC events and messages. As you can see the Windows needs your permission to continue User Account Control dialog box displays a four-color shield on a blue-green banner.