User Account Control (UAC) is a security component that allows an administrator to enter credentials during a non-administrator's user session to perform occasional administrative tasks without having to switch users, log off, or use Run As Administrator.  

Step-by-step guide

DISABLING USER ACCOUNT CONTROL FOR WINDOWS 7 AND WINDOWS SERVER 2008 R2:

1. Press Windows key and E key together. 
    

2. In the Windows Explorer Address Bar just type in Control Panel\User Accounts\User Accounts  without quotes and press enter. 
    

3. In the User Accounts window, click Change User Control Settings.
    

4. In the User Account Control Settings pane, under Choose When to Be Notified about Changes to Your Computer, pull the slider down to Never Notify. 
    

5. Then click OK. 

DISABLING USER ACCOUNT CONTROL FOR WINDOWS 8 AND WINDOWS SERVER 2012

1. Press Windows key and X key together. Windows key is the key between the Control and Alt key on the left hand side of the keyboard with a  sign on it. 
    
2. On the Power Menu, click Search. 
    
3. Type in Change in user settings , without quotes and choose Settings, press Enter. 
    
4. In the console, choose Never notify to disable it. 
    
5. Click OK.