I have used this website for several years now. The site will test your computer for security holes. It will even tell you how to go about plugging up the holes.
There is another messenger program, the Windows "Messenger Service", that comes with windows that many people do not know about. This is different then the "MSN Messenger" that is so popular. To make sure this program is disabled, there is a program call "Shoot The Messenger" that will disable this "Windows System Messenger Program" for you. You can get it here: http://www.grc.com/stm/ShootTheMessenger.htm