A/V : Avira is great (free edition is what I use). TBH, it's perhaps the only free a/v that has worked without any hitch whatsoever for me.
MSE would be a second choice, but I've run into some issues with it on my XP desktop previously, no problems on the laptop so far.
Defragger: Diskeeper 2010 is perhaps the best (not free unfortunately). For strictly free, windows defragger is what I'd pick.