Norton 2005 will probably cover you better against adware, spyware and Trojans. Make sure to enable scanning within compressed files, and max out the Heuristics. You can password-protect the options, which can be nice for a family PC so your teenager can't switch it into Nerf mode or disable the protection altogether when it keeps deleting... mmm, that one file, the one he/she's trying to download
By default, it seems Norton Antivirus 2005 will disarm the Windows Firewall (!) and use its wormstopper feature in place of it. You can override that behavior if you want.
I used AVG Free 7 for a while with no complaints, although my web surfing doesn't take me anywhere dangerous. I just tried a Norton 2005 15-day trial and am now trying McAfee VirusScan 9.0. Cannot... decide!
