User Account Control helps prevent potentially harmful programs from making changes to your computer, any changes that are made that require administrative permission will result in the following dialog box so you can confirm that this action can go ahead or cancel it if you did not choose to make that change

 

The dialog box will tell you what software is making the changes and where the software originated from so you can make an informed choice

 

 

You can adjust the settings for User Account Control from within the User Accounts section in Control Panel, but I would advise leaving the settings at default to protect your computer