Are you having any specific problems?
I would say try norton if you are just paranoid and want something easy to use. If you are really paranoid, would also recommend a router. In the experience with my router in the 6 months or so I have had it....it would rate it a must have....but I am big computer geek. And I hate norton....I just back up my important stuff on cds just in case....If I get a virus.....FORMAT AND WIPE TIME....lol. But hasn't happened yet.
There is a free scan available at
http://housecall.trendmicro.com/
Recommended by PCWorld also....which I use from time to time. They are the makers of PCcillin, which I believe is free with a Maxtor hard drive purchase.
The following link is a list at PCworld with reviews on various Anit-V Software.
http://pcworld.pricegrabber.com/search_ ... c2ebe35ce0
If you decide to buy one, recommend doing some price compares cause they don't always list the best prices.
Hope it helped!