anti-virus and such suggestions

OK so my Norton Internet security is about to expire and I am tired of the amout of PC resources that it takes up. I am also getting prepped to build a new Conroe PC so I am thinking if I should switch now is the best time. So please list any suggestions for anti-virus/software firewall/etc.

Thanks in advance for any help.

Get AVG, free edition.  www.grisoft.com

It's not perfect (doesn't seem to catch adware/spyware on my mom's computer that Ad-Aware did), but as far as free AV software is concerned, it's probably the best.