Hi, I have a question here!

Recently I have got myself a new computer and I'm currently using Windows Vista Home Basic. As security measures, I have installed SpyBot, Ad-Aware SE Personal and Spyware Blaster. I also have the avast! Antivirus Professional Edition which came along with the computer when I first bought it. Now I plan to install SpywareGuard which I have heard that it's a good addition to the SpywareBlaster. But then I have also heard that when more is installed than what is needed, it may result in an opposite way, which may lead to computer crash, etc. So now, I would like to know whether if it is all right for me to install the SpywareGuard. Thanks in advance! ^__^