AVG...he he he... dont bother.
I use Norton IS 2005, as it really does handle script blocking very well, and other highly customisable features which I need. I didnt really liike 2006, too much going on that I didnt need.
If you buy Norton(or any similar proggie), you usually get 12 months subscription. This means you can update program content, virus defs etc online autiomatically. After teh 12 months is over you can either - update to the next version, or renew the 12 months subscription(which is of course cheaper)/
If you really want a GOOD free AV proggie, go with AVAST
and whatever you get, make sure you also run
*An Anti-Spyware program, like Spybot
*A registry cleaner. A decent free one is TweakNow
...keeping a clean registry is very important - not only for weeding out entries associated with spyware/adware/malware(even if theyve been removed elsewhere) but keeps your startup time nice and trim. TweakNow is OK, but for a little $$$ you can get Registry Mechanic
which has an awesome deepscan mode, dregding up things you think you'd gotten rid of months/years ago. eg. old game installation entries for games that have been long uninstalled.