The good thing about antivirus, anti-spyware, and firewall applications is that once they're running fairly constantly and updating regularly, they don't need much babysitting, and chances of getting the nasties are way down.

Since I've started using a popup blocker, I've had no problems with trojans. Any operating system worth it's salt will have a way to block popups. If it doesn't, grab the Google popup blocker on the Google tools page. It has no spyware and is very cooperative and low-maintenance.

Teresa