Microsoft has been criticized by users that its earlier operating systems are not secure. So Microsoft introduced a new featureUser Access Control (UAC) with Windows Vista to improve the security of your system. This ensures that accidental system changes are not performed without your consent. If any kind of important system change is taking place by your action then it will ask for your permission by showing a dialog box. 

If you are logged on as a standard user and not as an Administrator and you are installing a new application, making changes to registry or writing to important system locations then Windows System asks for administrator credentials to avoid unauthorized or accidental changes. 

However Microsoft recommends "do not turn off UAC for security reasons". Even if you want to disable then please ensure that you have proper security measures in place like updated antivirus.

In Windows 7 Microsoft made the UAC less annoying and more controllable by providing a slider to set the notification level and disable it. Using this slider you can set the notification level you want from the following four options

Always notify

Notify me only when programs try to make changes to my computer

Notify me only when programs try to make changes to my computer (do not dim my desktop)

Never notify

This article tells how to disable UAC in windows 7 using Control panel

 GO toControl Panel.

Go to the  System and Security

In Action Centre click on  Change User Account Control Settings

Move the slider to lowest point“Never Notify” position Click ok. Provide confirmation if asked

Restart your System to apply changes.

Or in simpler way type UAC in Control Panel Search it will take you directly to the task "User Accounts – Change User Account Control Settings."

Enable UAC again by moving the slider to a desired position