a-squared Anti-Malware
Comprehensive PC protection against Trojans, Viruses, Spyware, Adware, Worms, Bots, Keyloggers, Rootkits and Dialers.

• Click to view attachment Cutting-edge Cleaning Scanners in 1: a-squared Anti-Spyware and Ikarus Anti-Virus engine
• Click to view attachment Malware Guards : Signature scan + Behavior Analysis
  
• New Surf Protection + Cookie Blocker - is able to block connection attempts to known dangerous hosts

Unlike conventional protection systems a-squared Anti-Malware does not only check signatures for known Malware patterns before starting a program, but it also constantly monitors the behavior of all active programs and raises an alarm as soon as something suspicious happens. Typical ways of infection are disabled in advance. Websites that try to plant Trojans or Spyware or that offer deceptive contents are blocked by the surfing protection. Signature updates at least 5 times per day, in combination with the zero-day protection of the behavior analysis - this guarantees the best possible
protection from new infections.

Supports: Win XP, 2003 Server, Vista and 2008 Server
(Older systems: v. 3.5 available - uninstall existing version and download the new 9x Edition. It will be maintained for a while - no new features added.

Product Info: a-squared Anti-Malware

a-squared Free
For Windows XP, 2003/2008 Server and Vista; Limited functionality on x64 . This program contains only the basic scanner.
http://www.emsisoft.com/en/software/download/

a-squared Free 4.0 will no longer run on Win 98/ME/2000
Version 3.5.0.37 - 9/21/2008 - for Windows 98, ME and 2000, download link right under
a-squared 4.0 - http://www.emsisoft.com/en/software/download/

2010-03-21 22:52:
There have also been numerous additional updates.
http://www.emsisoft.com/a2/changelog/free/
http://www.emsisoft.com/en/support/malware/