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! 😕