✔ 最佳答案
Tere are plenty oif good choices, but as you only asked ONE for each, I will give you the best choice only. I am using them for myself as well.
Free anti-virus: Active Virus Shield
www.activevirusshield.com
This is a version of the famous Kapasky anti-virus, good and reliable protection, does not significantly slow down your PC, and update every 2 hours. You need to register your email address to activate the products. (No worry, it will not send you advertisment or spam).
Free firewall: Zonealarm
www.zonelab.com
This is probably the most famous personal firewall software. Good protect and easy to use. However, this may slow down your PC a bit.
Actually, the bult-in Windows Firewall in XP Service Pack 2 is an OKAY choice if you do not require very high security...
Wish this can be helpful to you.