I was curious what some of you longtime members and everyone else has to say about how many antivirus,antispam/trojan,firewalls that you can install without problems. On any OS (mainly xp sp1 or 2)

And I ask this becuase I have had problems in the past with some combo's on xp sp1. So come on all lets here it!! And we all know about keeping current and Im not so much interested about all the tricks and tips just what your running?