I sue Kaspersky Antivir Pro, and Hitman Pro 2 (its a cool script/tool, it runs &  (if chosen in settings) installs ad-aware, Spybot S&D, Spyware Doctor, CWShreader, Hitman Antispyware, Webroot*,  Trend Micro SysClean*, McAffee VirusScan*. Plus its does a system cleanup and heuristic anylisis) 
[* i dont use cuz its shareware]
I would suges AVG Free for free Av though
Hitman Pro Link (German Site)