Just joined the forums, and thought I might add a bit for anyone reading this. To start off, I'm a network engineer for a national ISP, and deal with a network node that has almost 20,000 end users.
AVG is great, and so is Avast! antivirus. They are free for personal use, and smaller than norton or macafee, so they impact your computer less.
As far as anti spyware programs go, I lean towards "spybot search & destroy", and "Ad Aware SE". Both are available in free or trial versions, and when used in conjunction, they catch almost all of the nasty stuff out there. microsoft defener is also a great free add-on.
If anyone has any PC or networking questions (platform independant), feel free to email me. I try to check this account every few days.