I often go to a clients pc that “has anti-spyware installed” only to find they’ve clicked and installed on a popup that appeared whilst they were browsing. This list of rogue antispyware software is a good quick reference as to which spyware solutions are valid. Personally I only recommend search and destroy, adaware, microsoft’s AntiSpyware or Counterspy (although i’ve not actually used the latter one I know it has been getting good reviews and it is made by a reputable company)