I use Sygate Personal Firewall and Avast Antivirus. Can only be obtained by download:
Sygate Personal Firewall:
http://smb.sygate.com/products/spf_standard.htm
Avast AntiVirus Home Edition:
http://www.avast.com/eng/desktop_protection.html
Both are free, but they do 'Pro' versions for a small charge.
Both easy to update signatures and definitions which are small.
Sygate updates are not frequent but it's the AV updates which are more important, and Avast supplies updates several times a week, unlike Norton which only sends out virus updates once a week via liveupdate.
The 'Pro' versions are worth paying for. Still loads cheaper than Norton and just as effective as Norton as far as my experience of them is concerned. And nowhere near as demanding on system resources. Hope this advice helps u.