Why you should not run your computer as an administrator
Running your computer as a member of the Administrators group makes the system vulnerable to Trojan horses and other security risks. The simple act of visiting an Internet site or opening an e-mail attachment can be damaging to the system. An unfamiliar Internet site or e-mail attachment may have Trojan horse code that can be downloaded to the system and executed.
If you are logged on as an administrator of a local computer, a Trojan horse could reformat your hard drive, delete your files, and create a new user account with administrative access.
On a local computer, it is recommended that you add your domain user account only to the Users group (and not to the Administrators group) to perform routine tasks, including running programs and visiting Internet sites. When it becomes necessary to perform administrative tasks on the local computer, use Run as Administrator to start a program using administrative credentials.
You can use Run as Administrator to accomplish administrative tasks without exposing your computer to unnecessary risk. For more information, see Using Run as (http://go.microsoft.com/fwlink/?LinkId=28314).
For more information about how to use Run as Administrator, see Run a program with administrative credentials.
If you need to perform other administrative tasks, such as upgrading the operating system or configuring system parameters, log off and then log back on as an administrator.