You should choose the soft you use more carefuly.
Kazaa is evil, i wonder why so many people still use .
You should think about some open source alternatives. Like Bit Torrent and Direct Connect ++(i like the RevConnect mod).
But Kazza isnt the only cause. Another very evil thing is Internet Explorer. Firefox and Opera are much better. Never install evil shaware programs and other \"free\" commercial crap, they often contain spyware, i always search for Open Source alternates, because they never contain such evil things. mIRC is also evil, use X-chat insted.
So far the only free commercial program i like is Skype.