We don't bother with Defender in XP; Vista's version seems to be a little better, although that might just be an artifact of running on newer machines. I haven't had a chance to play with Windows 7 yet, unfortunately.
Avira by itself has been fairly successful for us (but we also encourage clients to use Firefox+AdBlockPlus, which stops a popular virus vector). The only hiccup we've had was with a new version of "Windows Security 2009" that slipped past Avira for a couple of days and spread by Outlook address books. MalwareBytes didn't find it either, but fortunately it's easy to remove manually.
The little bit that I've worked with SpywareGuard, I've liked it, with the caveat that it can require a lot of user interaction during software installs.
Avira by itself has been fairly successful for us (but we also encourage clients to use Firefox+AdBlockPlus, which stops a popular virus vector). The only hiccup we've had was with a new version of "Windows Security 2009" that slipped past Avira for a couple of days and spread by Outlook address books. MalwareBytes didn't find it either, but fortunately it's easy to remove manually.
The little bit that I've worked with SpywareGuard, I've liked it, with the caveat that it can require a lot of user interaction during software installs.
Haven't used SpywareBlaster.