Firewall and Antivirus question!

Which Antivirus and Firewall software do you consider the best?

Until now i thought that norton antivirus and zone alarm pro was the best but some teacher of mine told me that those two are firstly non free software and secondly that they require too much memory to run on my win xp system.

He suggested that i should download free software which are very good and light for my memory and system. So he told me to download AVG as for antivirus and Sygate Personal firewall for firewall which he says that is the best free products out there.

I am just wondering if i did well uninstalling Norton untivirus and zonealarm for those two products he suggested me so i decided to ask you guys this question?

Did i chosed well??

Maybe you have in mind something better and free?

this is all my opinion, take it at that. kerio's firewall is extra light on resources, and easy to configure, networking is supported, and is free. i use it on all my systems. http://www.kerio.com/us/kpf_home.html

as for anti virus, the only reason i use them is so they dont allow anything to change the mbr and to scan new files before i open, most every virus program can be bypassed by some virus, i use the free avg from http://www.grisoft.com/ on my home machines, at work the boss wants norton, which has failed us many times. i have used panda, norton mcafee, rav, trend, and a few dozen others, they all have something i do or dont like, to me avg is just as good.
also security in mind make sure you have a good spyware scanner like spybot search and destroy or adaware.