Another reason not to trust "free" proprietary software:
file sharing program KaZaA contains a
secret P2P application
which will resell your CPU cycles and bandwidth to KaZaA's corporate clients; essentially, this will use your Windows PC as part of a distributed ad serving network. They say that they'll let users opt out of this, but that's not what the licensing agreement says (unless "opting out" involves getting rid of KaZaA altogether).