Is it necessary to upgrade software firewalls such as Zonealarm 4.5??

I dont know about all these firewalls. I like zonealarm but the new ones seems like such bloated softwares that do everything….firewall, virus scan, spyware detector, and pop up blocker. It slows my computer down.

So I am curious why it’s necesssry to upgrade to a newer firewall if the old one blocks ports just fine.

Also, I am thinking of upgrading to Vista, that means the old zonealarm 4.5 probably wont work with the new OS and I’ll be forced to upgrade to the newer bloated versions?