avast! Free Antivirus

"Free antivirus for non-commercial home use- scans for all malware types"

Avast Home Edition is a complete ICSA & Checkmark certified antivirus, Checkmark certified anti-spyware & anti-rootkit package. Avast includes the following components: On demand scanner with skinnable simple interface, just select what do you want to scan in which way and press the Play button; On access scanner, special providers to protect the most of available e-mail clients; Instant messaging--ICQ, Miranda; Network traffic--intrusion detection, lightweight firewall; P2P protection for Kazaa, BitTorrent; Web shield--monitors and filters all HTTP traffic; NNTP scanner--scans all Usenet Newsgroup traffic and all operations with files on PC; Boot time scanner--scans disks in the same way and in the same time as Windows CHKDSK does.

Note: You'll have to register (free) on the publisher site to be able to continue using this program after 60 days