Avast antivirus (I have just this running at the moment on the laptop)
Spybot Search and Destroy
i think they were working pretty well. Though I did not really understand most of Comodos messages, everything seemed to be a potential threat! Also Spybot's log after a search confused me and i removed nothing!
Anyway I have 2 or 3 of the latest DVDs from PC mags with practically every free security programme available, so i would welcome recommendations as to what to install.