Look no further than Nod32, ive tried about 3-4 different antivirus programmes that people have said are good and none of them were as good as nod32.
Ive been using it for about 7months now and my pc is spot on, its simple to use, and it doesnt slow a pc down at all, oh and it updates everyday, sometimes even twice a day, ive got nothing bad to say about it check out there site http://www.eset.com/

Its not free by the way but nothing worth having comes for free

For firewall ive always used Zonealarm, agian this doesnt slow a pc down and its very good