I have in the past used a personal firewall (Zonealarm) very happily. However, recent versions seem to cause a lot of instability on XP. I have seen some advice to replace the functionality with a SPI router.
My question: does not the software firewall still provide additional protection against trojans that try to "phone home?"
I am evaluating the latest Zonealarm update to see if they have cured the instability problems. I am also moving to install Linksys WRT54GS wireless routers with built-in SPI.