MalwareBytes AntiMalwareMalwarebytes Anti-Malware is one of the most powerful anti-malware applications available today. While the free version is fantastic, we recommend purchasing the professional version to help curtail future attacks.
Home Page: http://www.malwarebytes.org/mbam.php

Avast is simply one of the most comprehensive antivirus packages available today. Avast offers a free version for non-commercial use and offers great pricing for businesses.
Home Page: http://www.avast.com/index

Microsoft Security Essentials is a new (2010 released) free product from Microsoft that provides real-time protection for your PC from viruses, spyware and malware.
Home Page: http://www.microsoft.com/Security_Essentials/
AVG Antivirus is a comprehensive security suite for home users (free) and professionals. It is a great low-footprint package with all the features of the big-name providers like Norton and McAfee.
Home Page: http://free.avg.com/us-en/homepage
Super AntiSpyware is a great lightweight application for removing malware, spyware and trojans that other applications seem to often miss. It has similar functionality to MalwareByte’s Anti-Malware.
Home Page: http://www.superantispyware.com/
ComboFix is an extremely powerful rogue remover designed for a last-resort situation. Before using ComboFix, it is essential that you read the accompanying guide.
Guide and Download Page: http://www.bleepingcomputer.com/combofix/how-to-use-combofix
HiJackThis is a free tool from Trend Mirco for dignosing problems caused by malware. It generates an in depth report of registry and file settings from your computer. HijackThis makes no separation between safe and unsafe settings in its scan results giving you the ability to selectively remove items from your machine. In addition to this scan and remove capability HijackThis comes with several tools useful in manually removing malware from a computer.
Home Page: http://free.antivirus.com/hijackthis/