Without a doubt, Lavasoft Ad-Aware is the most performant and popular anti-spyware free software out there! There also are paid versions of this anti-spyware software but for a pc/laptop that you use at home, the free version offers enough protection against Internet attacks.
Lavasoft Ad-Aware 2008 details:
– protection against trojans, worms, spyware, bots and other malware attacks with the help of CSI technology.
– rootkit identify and destroy system
– integrated TrackSweep system. This service erases saved passwords, cookies, history and any other tracks you leave behind while surfing the net. It was Opera, Internet Exporer, Firefox, Safari browser support.
– Lavasoft ThreatWork – this service allows you to send suspicious files to Lavasoft for analysis.
– System Restore Point – the files that were altered during a malware attack can be restored.
– Free unlimited updates that include the latest protection solutions against the newest spyware and malware threats.
– Lavasoft Anti-Spyware has an intuitive graphical interface, easy to install and configure.
You can download this software here: http://www.lavasoft.com/single/trialpay.php