User Account Control (UAC) is a facet in Vista that can help avoid unlawful modifications to PC. UAC does this by asking you for consent or an administrator password before performing actions that could potentially change PC's process or modify settings that change other users.

UAC will provide warning with one of the following messages:

Windows wants your permission to continue
A Windows function or program that can alter other users of PC needs your consent to start. Ensure that it is a function or program you want to run.

A program needs your permission to continue
This will occur when a program that is not part of Windows wants your permission to begin. It has a valid digital signature signifying its name and publisher, which helps to make sure that the program is what it utters to be. Ensure that this is a program that you intended to run.

An unidentified program wants access to your computer
This is caused by a program that administrator has chiefly blocked from operating on PC is attempting to run. To run this program, you should have a manager unblock it.
The main cause to build employ of UAC is to avoid malware and spyware from installing or making modifications to PC without consent. This comes in useful when you have consumers who may go to wrong websites or download software from Internet that possibly of risk to PC.

If you trust customers or if it’s just you that will be using PC and you are certain that you will not be installing anything you should not then you can turn this facet off.
Here is how you turn User Account Control facet off.
1. Open consumer Accounts from Control Panel.
2. Tick on turn consumer Account Control on or off.
3. Uncheck the box that shows Use consumer Account Control (UAC) to help protect your computer.
4. Tick Ok. You have to enter manager records based on who you are logged in as.
5. Reboot PC for modifications to obtain effect.